444 WILSON. [Vol. XI. 



I shall endeavor to show, however, that even this difference, if 

 it really exist, is probably of minor importance. The main 

 purpose of this paper is, however, to record certain observa- 

 tions upon the structure and origin of the archoplasmic struc- 

 tures in Toxopneiistes, and their relation to the centrosome and 

 the chromatin, that diverge to some extent from Boveri's, and 

 lead to a conception different from his.^ 



I. The Archoplasm. 



Boveri's paper raises questions of the greatest interest re- 

 garding the relation of the archoplasm to other constituents of 

 the cell, and they are of special importance, since he still main- 

 tains on the whole his original views, based on the study of 

 Ascaris, which are opposed to those of Heidenhain, Reinke, 

 and a number of other recent workers. Since it is to Boveri 

 that we owe both the conception of the archoplasm and its 

 name, it may be useful to recall briefly the statement of his 

 original views and their recent modification. 



As first employed in the second of the classical "cell-studies" 

 the term "archoplasm" was applied to "that substance of the 

 cell which at the time of division forms the achromatic nuclear 

 spindle and the two polar astral systems" (I.e., p. 6i). On 

 the basis of Van Beneden's discovery and his own that the 

 centrosome persists throughout the "resting stage" of the cell, 

 and may therefore be considered as a permanent cell-organ, he 

 developed the archoplasm-conception clearly and logically as 

 follows. The archoplasm is a specific substance, distinct from 

 the remaining cell elements (p. 62), which in the resting cell 

 may be scattered through the cell-substance or may be aggre- 



1 The accompanying photographic illustration and most of the text-figures are 

 selected from a much larger series now in course of publication as an " Atlas of 

 Fertilization and Karyokinesis of the Ovum " by the Columbia University Press 

 (Macmillan & Co., N. Y.), to whom my thanks are due for permission to reproduce 

 them here. Most of the observations here recorded were made (like the photo- 

 graphs) on sections of eggs fixed in sublimate-acetic and stained on the slide with 

 iron hasmatoxylin, followed in many cases with Congo red or acid fuchsin. The 

 sections thus obtained are of brilliant clearness and are far superior to those pre- 

 pared by other methods tested (sublimate, Hermann's fluid, chrom-acetic, picro- 

 acetic, picro-osmic, picro-sublimate). 



