DEVELOPMENT OF PLATYPHVLAX. 59 



nuclear history as outlined. The granules in the large nuclei are 

 of about the same actual size, with the same inter-granular spaces, 

 as in the young rounded nuclei. No evidence was noted in the 

 staining reaction which might lead to the conclusion that those 

 of the younger nuclei were merely more dense. Indeed, the dif- 

 ference in size of the nuclei is so great that it is almost impossible 

 to conceive of the chromatin of one of the large nuclei being com- 

 pressed or condensed to the relatively few granules found in a 

 small one. The chromatin must therefore increase in amount. 

 In all stages a linin reticulum is easily distinguishable with the 

 higher magnifications, particularly in sections. 



Conclusions. 



1. The larger particles of stainable material in the spinning- 

 gland nuclei of P. dcsignatus are derived by division and growth 

 from an original nucleole of normal type and hence may be re- 

 garded as true nucleoles. 



2. The red-staining granules in the nuclei of similar glands of 

 lepidoptera, whether larger than the chromatin granules or not, 

 are probably of similar origin and character. 



3. This nucleolar material increases in amount with the growth 

 of the nucleus. 



4. The latter conclusion coupled with one in a former paper 

 (Marshall and Vorhies, 1906, p. 417), that the nucleoles become ir- 

 regular as a result of glandular activity, leads to the further con- 

 clusion that the nucleolar material bears a direct relation to such 

 activity: whether as a waste product or as a material functional 

 in secretion I make no assertion.^ 



5. The chromatin increases in amount with the growth of the 



' In connection with conclusion 4, attention may be called to the following from 

 Montgomery (1899), P- 537- " The hypothesis might be suggested that though the 

 nucleolus probably consists of substances which stand in some relation to the nutritive 

 processes of the nucleus, and so at the time of its formation may be a functionless, 

 inert mass of substance, yet it may at later periods in the history of the resting 

 nucleus acquire some active function and thus gradually come to acquire the value of 

 a nuclear organ ; this hypothesis is put forward merely as a tentative one. Accord- 

 ing to this view the nucleolus might be considered as an organ which serves to accumu- 

 late in itself the waste products of the nucleus, thus serving as a reservoir for such 

 substances ; or it might be considered as an organ of excretion, to discharge waste 

 products out of the nucleus ; in either case the nucleolus would seem to stand indirect 

 connection with the nutritive substances and forces of the nucleus." 



