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    Such a doctrine is , in fact , a most obvious and almost a necessary development of the doctrine of epigenesis in general . To one who had worked out the conclusion , that the most complex , grosser , animal or vegetable organizations , arise from a semi-fluid and homogeneous mass , by the continual and successive establishment of differences in it , it would be only natural to suppose that the method of nature , in that finer organization which We call histological , was the same ; and that as the organ is developed by the differentiation of cells , so the cells are the result of the differentiation of inorganic matter . If the organism be not constituted by the coalescence of its organs and tissues in consequence of their peculiar forces , but if , on the other hand , the organism exists before its organs and tissuss , and evolves them from itself , —is it not probable that the organs and tissues also , are not produced by the coalescence of the cells of which they are composed , in consequence of their peculiar forces , but , contrariwise , that the cells are a product of the differentiation of something which existed before them ?

    " For Schwann the organism is a beehive , its actions and forces resulting from the separate but harmonious action of all its parts ( compare Schwann , 1 . c , p . 229 ) . For Wolff it is a mosaic , every portion of which expresses only the conditions under which the formative power acted , and the tendencies by which it was guided . " Here , while upholding the doctrine of Epigenisis , he expresses that of Evolution , for he conceives the organism to exist before its organs , and to evolve them from itself ! "What is that but the doctrine of pre-existent germs evolving into organisms ? Then again , he asks whether the cells are not products of the differentiation of " something" which existed before them . Assuredly . Schwann would be equally emphatic in maintaining such a position ; but he would add the " something" is not an organism , because an organism is the sum total of its organs . There are other indications of a metaphysical tendency , but we pass on to the criticism of the cell-theory . Mr . Huxley undertakes to establish the error of these three fundamental positions assumed by Schleiden and Schwann : —

    " 1 . The prevalent notion of the anatomical independence of the vegetable cell , considered as a separate entity . " 2 . The prevalent conception of the structure of the vegetable cell . " 3 . The doctrine of the mode of its development . " His remarks on the first count are , in our opinion , to be rejected as inconclusive , and opposed by the strongest evidence . The vegetable cell is independent , and dependent also ; just as human beings are independent , yet considered as parts of the social organism they are mutually dependent . A cell may live isolated , or in aggregation with others , just as a man may . And the biological series displays , immense varieties in the gradation of dependence , so that in the complex organisms the individual cell has lost its power of independence merged in a dependence on a higher life . Schwann's remai'ks on this point are so good , that the reader will thank us , if we take the volume from our shelves and quote them : —

    " We have seen that all organized bodies are composed of essentially similar parts , namely , of cells ; that these cells are formed and grow in accordance with essentially similar laws ; and , therefore , that these processes mugt , in every instance , be produced by the same powers . Now , jf we find that some of these elementary parts , not differing from the others are capable of separating themselves from the organism , and pursuing an independent growth , we may thence conclude that each of the other elementary parts , each cell , is already possessed of power to take up fresh molecules and grow ; and that , therefore , every elementary part possesses a power of its own , an independent life , by means of which it would be enabled to develop itself independently , if the relations which it bore to external parts were but similar to those in which it stands in the organism . The ova of animals afford us examples of such independent cells , growing apart from the

    organism . It may , indeed , be mud of the ova of higher animals , that after impregnation the ovum is essentially different from the other cells of the organism ; that by impregnation there is a . something conveyed to the ovum , which is more to it than an external condition for vitality , more than nutrient matter ; and that it might thereby have first received its peculiar vitality , . and therefore that nothing can be inferred from it with respect to the other cells . But thin fails in application to those classes which consist only of female individuals , as well as witli the spores of the lower plants ; and , besides , in the inferior ' plants any given cell may be separated from the plant , and then grow alone . So that here arc whole plants consisting of cells , which can bo positively proved to have independent vitality Now , as all colls grow according to the name laws , and consequently the cause of growth cannot in one case lie in the cell , . and in another in tho whole organism ;

    and Hincc it may be further proved that hoiiio cells , which do not differ from the rest in their modo of growth , are developed independently , we must ascribe to all cells an independent vitality , that is , snob combinations ' of molecules an occur in any single cell , are capable of setting free tho power by which it fa enabled to take up fresh molecules . I lie cause of nutrition and growth residea not in tho organism as a whole , but in the separate elementary parts - the cells . The failure of growth in tho case of any particular cell , when separated from an organized body is as slight an objection to this theory , as it is an objection against the independent vitality of a bee , that it cannot continue long j a existence after being separated from itH Hwann . Tho manifestation of tho power wliieli resideH in the cell depends upon conditions to winch it is subject only when in connexion with the whole ( organism ) . "

    The second and third counts , namely , respecting tho structure and development , of the vegetable coil , Mr . Jluxley proven with Huecesn The discovery of tho primordial utricle by Hugo von Mohl necessarily altered the aspect of the whole queHtum . Sehwann , however , knew oftho oxistoncc of cells without nuclei , and regarded the nucleus as a primary cell and we will here give his explanation :- —« '

    " Tho fact that many nuclei are developed into hollow vesicles , and the difficulty of distinguishing no mo of these hollow nuclei from cells , form ' s quito Huflicient ground for tho ( supposition that a nucleus does not dilFor essentially from n coll ; that an ordinary nucleated coll in nothing more than a cell formed around the outside of another cull , the nucleus ; and that the only riiHorenoo between the two contents in tho inner one being more slowly and less completely developed after tho external one hao been formed around it . if ( , his description w « , <; orro ' et wo might express ourselves with more precision , and designate the nuelei as colls of tho firnt order , and the ordinary nucleated colls as cells of tho sooond order Hitherto wo have decidedly maintained a distinction botwoen cell and nucleusand it was convenient to ( Jo ho as long- as we were engaged in merel y describing the ol > Horvatioiin . There can bo no doubt that tho nuclei correspond to one another in all coIIh ; but the designation , ' cells of tho first order , ' includes a theoretical viow of tho mutter which ha , n yofc to bo proved , nauioly , tho idontity of

    development . The cell- membrane increases in its superficies , and often in thickness also , and separates from the nucleus , which remains lying on the wall ; the membrane of the hollow cell-nuclei grows in the same manner , and the nucleolus remains adherent to a spot upon the wall . A transformation of the cell-contents frequently follows , giving rise to a formation of new products in the cell-cavity . In most of the hollow cell-nuclei , the contents become paler , less granulous , and in some of them fat-globules , &c , are formed . We may therefore say that the formation of cells is but repetition around the nucleus of the same process by which the nucleus was formed around the nucleolus , the only difference being that the process is more intense and complete in the formation of cells than in that of nuclei . "

    the formative process of the cell and the nucleus . This identity , however , is of the greatest importance for our theory , and we must therefore compare the two processes somewhat more closely . The formation of the cell commenced with the deposition of a precipitate around the nucleus ; the sa"me occurs in the formationof the nucleus around the nucleolus . The deposit becomes defined externall y into a . solid stratum : the same takes place in the formation of the nucleus . The development proceeds no farther in many nuclei , and we also meet with cells which remain stationary at the same point . The further developmentof the cells is manifested either by / the entire stratum , or only the external part of it becoming consolidated into a membrane ; this is precisely what occurs with the nuclei which undergo further

    After reading this passage we can accept what Mr . Huxley says , without its greatly altering Schwann ' s theory : — et Since , then , the functions of the vegetable ' cell' can be effectually carried on by the primordial utricle alone ; since the ' nucleus' has ' precisely the same chemical composition as the primordial utricle ; and since , in some cases of celldivision , new nuclei are seen to arise in the substance of the endoplast , by a mere process of chemical and morphological differentiation ( Von Mohl , 1 . c , p . 52 ) , it follows , we think , that the primordial utricle must be regarded as the essential part of the endoplast—the protoplasm and nucleus being simply its subordinate , and , we had almost said , accidental anatomical modifications . " We cannot enter further into details , but refer to Mr . Huxley ' s paper , and conclude these observations with an extract or two from his speculative passages : — WHAT ABE CELLSP

    "What is the meaning of - the unquestionable fact , that the first indication of vitality , in the higher organisms at any rate , is the assumption of the cellular structure ? ' '' In answering these questions , we would first draw attention to the definition of the nature of development in general , first clearly enunciated by Von Baer . ' The history of development , ' he says , 'is the history of a gradually increasing differentiation of that which was at first homogeneous . ' The yelk is homogeneous ; the blastoderma is a portion of it which becomes different from the rest , as the result of the operation of the laws of growth ; the blastoderma , again ,

    comparatively homogeneous , becomes differentiated into two or more layers ; the layers ^ originally identical throughout , set up different actions in their various parts , and are differentiated into dorsal and visceral plates , chorda dorsalis and bodies of vertebne , &c . &c . No one , however , imagines that there is any causal connexion ! between these successive morphological states . No one has dreamt of explaining the development of the dorsal and . visceral plates by blastodermic force , nor that of the vertebrse by chorda-dorsalic force . On the other hand , all these states ar& considered , and justly , to result from the operatio n of some common determining power , apart from them all—to be , in fact , the modes of manifestation of that

    power . " Now , why should we not extend this view to histology , which , as we have explained , is only ultimate morphology ? As the whole animal ia the result of the differentiation of a structureless yelk , so is every tissue the result of the differentiation of a structureless blastema — the first step in that differentiation being the separation o the blastema into endoplast and pc ? 'iplast , or the formation of what is called a ' nucleated cell . ' Then , just as in the development of the embryo , when the blastodermic membrane is once formed , new organs are not developed in other parts of the yelk , but proceed wholly from the differentiation of the blastoderm , — so hiatologically , the ' nucleated cell , ' the periplast with its endoplast , once formed , further development takes Tjlace by their growth and differentiation into now

    endoplasts and periplaBts . The further change into a special tissue , of course , succeeds and results from this primary differentiation , as we have seen tho bodies of tho vertebrae succeed tho chorda doraalis ; but is there any more reason for supposing- a causal connexion between tho one pair of phenomena , than between the other ? Tho cellular structure precedes the special structure ; but is tho latter , therefore , the result of a ' cell-force , ' of whose existence there is on other grounds no ovidenco whatever . We must answer in the negative . For us the primarily cellular structure of plants and animals is simply a fact in the history of their histological development—a histologically necessary atago , if one may so call it , which ban no more causal connexion with that which follows it , than tho equally puzzling morphological necessity for tho existence of a chorda dorsalis or of Wolffian bodies has , with the development of tho true vertebne or of the true kidneys . "

    We beg to add , in passing , that there is a causal connexion between tho chorda dorsalis and tho vertebra ) , tho Wolilian bodies and the kidneys . ( The reason is given in Comtc ' s Philosophy of the Sciences , p . 3 < 1 . ) TJIJO STJJUCTUUK OF PLANTS AND ANIMALS . " Vitality , the faculty , that is , of exhibiting definite cycles of change in form and composition , is a property inherent in certain kinds of matter . " There in a condition of all kinds of Irving matter in which it is an amorp hous germ—that is , in which its external form deponds merely on ordinary physical lawn , and in which it poHHessea no internal structure . " Now , according to the nature of certain previous conditions—tho character of tho changes undergone—of tho different fitatott neceasarily exhibited—or , othor words , the miecoHsivo differentiations of the amorphous mass will bo different .

    " Conceived jih a whole , from their commencement to their termination , they coriHtituto tho individuality of tho living-being , and thopansago oftho living being through those states , in culled H , h development . Development , therefore , and Hi « are , strictly speaking , one thing , though wo are accustomed to limit tho former to the progressive half of life merely , and to npealc of tlie retrogressive half au decay , considering an imaginary resting point between tho two aa the adult or perfect state . " The individuality of a living tiling-, then , or n . dingle lifo , in a continuous development , and development in the continual differentiation , tho constant cyclical ehango of that which was , at firat , morphologically and chemically , indifferent flnu homogeneous .

    " Tho morphological differentiation may ho of two kinds . In tho lowest animals and plants—tho Ho-eallod unicellular organisms— it may be Raid to be external , tho changed of for / n boing essentially confined to tho outward shape oftho germ , and being unaccompanied by tho development of any internal wtruoturo .

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    1074 THE LEADER . * [ Saturday ^

• Citation
  • Leader (1850-1860), Nov. 5, 1853, page 1074, in the Nineteenth-Century Serials Edition (2008; 2018) ncse-os.kdl.kcl.ac.uk/periodicals/l/issues/vm2-ncseproduct2011/page/18/