484 WARO NAKAHARA 



The question of the significance of amitosis has been much 

 debated for many years. This method of nuclear division was 

 regarded by many authorities to be associated with highly 

 specialized and pathological conditions, but some of the recent 

 writers hold the view that it is related to the rapid growth and 

 differentiation of the tissue, others believe that it is due to special 

 environmental conditions, and still others attribute the phenom- 

 enon entirely to certain mechanical processes. The chief object 

 of this paper is to discuss the subject in the light of the facts 

 observed in the adipose cells of insects, and to clear up the field, 

 if possible, by a careful review and comparison of hitherto ob- 

 served facts bearing on the subject. 



It is also hoped that this paper may be of some interest inso- 

 far as it is concerned with the histology and physiology of adi- 

 pose tissue of insects, since, although general features of changes 

 occurring in the cells during their activity, have been observed 

 by many authors, cytological and histochemical studies of the 

 subject have been rather unsatisfactory. 



This work was done in the Entomological Laboratory of Cor- 

 nell University under the supervision of Prof. Wm. A. Rilej^. 

 My deep obligation is due to Professor Riley for his encourage- 

 ment and help rendered me during the course of the work. I 

 also wish to express my thanks to the Department of Histology 

 and Embryology of the same Institution for the privilege of 

 using some of the equipment. 



II. MATERIAL Ax\D TECHNIQUE 



While many other insect larvae, especially lepidopterous, have 

 been used in preliminary work, and also for comparisons, Pieris 

 rapae is the one in which the entire subject has been worked out. 

 A large number of larvae, representing all the developmen- 

 tal stages were subjected to cytological and histochemical 

 examinations. 



For general cytological purposes, materials were fixed in 

 Bouin's picro-aceto-formol or Carnoy's chloroform-alcohol-ace- 

 tic ('6-3-1'), and sections were stained with Ehrlich-Biondi- 

 Heidenhain mixture, iron haematoxylin with or without orange 



