A Criticism of the Cell-Theory; being an Answer to Mr. Sedgwick's ...

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146 GILBERT 0. BOUBNE. enzirung der Individuen erster Ordnung, der Plastiden" (op, cit.j p. 222). Of animals he says, on the contrary, " Der wesentliche tectologische character der Thiere liegt sowohl in der verwickelteren Zusammensetzung der Thierleibes aus weit differenzirten Individuen verschiedener Ordnung, als auch besonders in der verschiedenartigsten Ausbildung der Individuen zweiter Ordnung, der Organe, welche viel mannichfaltiger, als bei den Pflanzen und Protisten, differenzirt und polymorph sind. Die Plastiden, die Individuen erster Ordnung, sind bei Thieren allermeist Zellen, und zwar meistens Nacktzellen (ohne Membran) weniger Hautzellen (mit Membran). Sehr haufig, und allgemein in den entwickelten Personen, vereinigen sich bei den Thieren mehjere Nacktzellen zur Bildung von Zellstocken (Nervefasern, Muskelfasem), was bei den Pflanzen nur bei der Bildung der Milchsaftgefasse und der Spiralgefasse geschiecht. Daher verliert bei den Thieren stets wenigstens ein Theil Zellen ihre individuelle Selbstandigkeit, wahrend sie dieselbe in den Pflanzen meist behalten." The last sentence, which I have put in italics, shows most clearly that, as long ago as 1866, Hackel did not regard the animal organism as a community, whose individuals are cells; and it is the fact that he applied the term " cell-republic " to plants, intending thereby to emphasise the difference which he believed to exist between vegetable and animal organisation. So that, as a matter of history, whilst plants used to be considered to be colonies of independent life units, animals were not. A certain exchange of opinion seems to have taken place more recently. Some few zoologists and animal physiologists, borrowing from Hackel the term cell-republic, have thoughtlessly applied it, with all its implications, to animal organisation, whilst botanists, influenced by Mr. Walter Gardiner's researches, have insisted more and more upon the individuality of the plant as a whole, and the subordination of its component parts, the cells. None the less, the facts of cell fusion and cell communication have never been wholly overlooked by zoologists, and recent years have brought to
A CRITICISM OP THE CELL-THEORT. 147 light facts, such as the continuity of cartilage cells, which were unsuspected when Hackel wrote. I am therefore far from being satisfied that the independentlife-unit theory has had such a dominant influence as Mr. Sedgwick would have us believe; and I am quite certain that the picture which he draws of the teaching given to every student of biology is a travesty of the truth. Biology includes botany as well as zoology, and if we were to allow (which I do not) that zoologists generally have become as narrow in their conceptions of the processes of development as Mr. Sedgwick says, it is quite certain that botanists have not. And as all students of biology are—or if they are not, they ought to be—put through a course of elementary botany as well as of zoology (in many schools the subjects are combined), grave blame must be imputed to those teachers who have, in the later stages of their education, Warped the liberal conceptions which they must have formed on the subject of organic growth and development. For I take it that, after a study of Mucor, Vaucheria, and the Myxomycetes, there is no student so dull but he will have imbibed ideas respecting cell growth which impel him to ask the question which as Mr. Sedgwick says it is so difficult to find an. answer to—" What, after all, is a cell?" If, when he asks this question, he is told that the cell is an isolated corpuscle of protoplasm, the unit of vitality, and that there is " a most fundamental distinction" between unicellular and multicellular organisms, and so forth, the student may go on his way rejoicing, for that he has at last been given a clear and tangible statement; but none the less he will have been started on a very wrong path. I have not a widespread experience of zoological teaching, but I know, at least, that Professor Laokester's pupils are not started on that path. The truth is, and, if I am not much mistaken, zoologists and botanists alike have long been possessed of it, that there is no fundamental but only a formal distinction between unicellular and multicellular organisms; that the cell is a form concept founded on a very wide basis of experience, whereby we can conveniently
Page 1 and 2: A OEITIOISM OF THE GULL-THEORY. 137
Page 3 and 4: A CRITICISM OP THE DELL-THEORY. 139
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Page 7 and 8: A CRITICISM OF THE CELL-THEORY. 143
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Page 35 and 36: A ORTTIOISM OP THE OELL-THEORY. 171

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