THE PRESENT POSITION OF CELL-THEORY. 107 



isation of separate living particles, the aggregate functions 

 of which produce the vital phenomena. It is further urged 

 in favour of this view of organisation, that in almost all 

 cells we are able to recognise structures under the micro- 

 scope each of which behaves in respect of growth and 

 multiplication in a manner analogous to that in which the 

 cell behaves. Not only the nucleus but also the chromatin 

 bodies, the microsomata of which these are composed, the 

 centrosomes, the green chromatophores of plant cells, may- 

 be observed to increase in size, i.e., to grow and to multiply 

 by division, and it is held that this is proof that the ultimate 

 particles composing these bodies must assimilate, grow and 

 divide in a manner similar to that in which cells assimilate, 

 otow and divide. 



This view, whilst receiving a considerable measure of 

 support from other sources, has been most energetically 

 supported by Wiesner, 1 whose extensive work on the subject 

 has received the weighty approval of Weismann. Wiesner 

 refers in detail to the various structures in the form of 

 granules or corpuscles which may be observed in animal 

 and vegetable protoplasm, and he attributes to one and all of 

 them the powersof assimilation and multiplication bydivision. 

 Nor does he confine himself to the living substance gener- 

 ally recognised under the name of protoplasm. He labours 

 at great length to prove that the cell wall, so often con- 

 sidered as an inert non-living product of living protoplasm, 

 is not in fact dead, but contains a living substance distin- 

 guishable under the name dermatoplasm, and ultimately 

 composed of structural elements of the same fundamental 

 nature as that of the cytoplasm. These ultimate particles 

 are the fi/asomes, which form the central point of his theory 

 of the constitution of living matter. Further than this he 

 accepts in full the theory of De Vries with regard to vacuoles, 

 and considers them to be just as much independent organ- 

 isms as the chromosomes, the centrosomes, the chlorophyll 

 bodies and other things. This theory of vacuoles, which 



1 J. Wiesner, Die Elementar structur und das Wachsthum der Lebendem 

 Substanz. Wien : Alfred Holder, 1892. 



