438 TRANSACTIONS OF SROTION D. 



of biological investigation termed cytology, which deals with cells in a general 

 manner independently of their provenance, whether animal or vegetable. 

 Some knowledge of the cell and its activities is necessary at the present time 

 for every one "concerned with the study of living things, whether that study 

 is pursued for its own sake and with disinterested objects, or with the 

 intention of applying scientific principles to practical aims, as in medicine or 

 aoriculture. One might have expected, therefore, that at least some elementary 

 understanding of the nature and significance of the cell, and the importance 

 of cellular activities in the study of life and living things, would have formed 

 at the present time an indispensable part of the stock of knowledge acquired 

 by all intelligent persons who are ranked as ' educated ' in popular estimation. 

 Unfortunately this is so far from being the case that it is practically impossible, 

 in this country at least, to find anyone amongst the educated classes to whom 

 the words ' cell ' and ' cytology ' convey any meaning at all, except amongst 

 those who have interested themselves specially in some branch of biology. 

 Consequently, any discussion concerning the cell, although it may deal with the 

 most elementary processes of life and the fmidamental activities and peculiari- 

 ties of living beings, ranks in popular estimation as dealing with some abstruse 

 and recondite subject quite remote from ordinary life and of interest only to 

 biological specialists. It must, however, be pointed out that the general state 

 of ignorance concerning these matters is doubtless in great part due to the fact 

 that" an objective acquaintance with cells cannot be obtained without the use of 

 expensive and delicate optical in.struments. 



I propose in this address to deal with an aspect of cytology which appears 

 to me not to have received as yet the attention which it deserves, namely, the 

 evolution of the cell itself and of its complex organisation as revealed by the 

 investigation of cytologisls. Up to the present time the labours of professed 

 cytologtsts have been directed almost entirely towards the study of the cell 

 in its most perfect form as it occurs in the Metazoa and the higher plants. 

 Many cytologists appear indeed to regard the cell, as they know it in the 

 Metazoa and Metaphyta, as the beginning of all things, the primordial unit 

 in the evolution of living beings. 3 For my part I would as soon postulate the 

 special creation of man as believe that the Metazoan cell, with its elaborate 

 organisation and its extraordinarily perfected method of nuclear division by 

 karyokinesis, represents the starting-point of the evolution of life. So long, 

 however, as the attention of c>i,ologists is confined to the study of the cells 

 building up the bodies of the higher animals and plants, they are not brought 

 face to face -with the stages of evolution of the cell, but are confronted only 

 with the cell as a finished and perfected product of evolution, that is to say, 

 with cells which, although they may show infinite variation in subordinate 

 points of structure and activity, are nevertheless so fundamentally of one type 

 that their plan of structure and mode of reproduction by division can be 

 described in general terms once and for all in the first chapter of a biological 

 text-book or in the opening lecture of a course of elementary biology. 



One of the most striking features of the general trend of biological investi- 

 gation during the last two decades has been the attention paid to the Protista, 

 that vast assemblage of living beings invisible, with few exceptions, to the 

 unassisted human vision and in some cases minute beyond the range of the 

 most powerful microscopes of to-day. The study of the Protista has received 

 in recent years a great stimulus from the discovery of the importance of some 

 of the parasitic forms as invaders of the bodies of men and animals and causers 

 of diseases often of a deadly nature; it has, however, yielded at the same 

 time results of the utmost importance for general scientific knowledge and 

 theory. The morphological characteristic of the Protista, speaking generally, 

 is that the body of the individual does not attain to a higher degree of 



' For example, my friend Dr. C. E. Walker, in an article in Science Progress 

 (vol. vii. p. 639), after stating that 'The unit of living matter, so far as 

 we know, is the cell,' proceeds to deal with 'that form in which it is found 

 in the multicellular and the majority of unicellular organisms, both animal 

 and vegetable ' and then describes the typical cell of the cytologist, with 

 nucleus, cytoplasm, centroaome, chrondriosomes, and reproduction with fully 

 developed karyokinesis. 



