62 ETHEL NICHOLSON BROWNE 



VI. Mitochondria 94 



A. Observations 94 



1. Late growth and division stages 94 



2. Early growth stages: nuclear plate 96 



B. Discussion 97 



Vir. Summary 98 



Literature cited 99 



L INTRODUCTION 



Gilson, in his study of the spermatogenesis of the arthropods in 

 1885, passed over Notonecta with the remark, ''Les phenomenes 

 de la spermatogenese y sont fort simples et presentent pen de parti- 

 cularites dignes d'etre mentionees" (op. cit., p. 123), adding that 

 N. glauca possesses the longest and largest spermatozoa known. 

 More recently, Pantel and Sinety ('06) have published a copious 

 memoir on ''Les cellules de la lignee male chez le Notonecta 

 glauca L.," and they, unlike Gilson, have found themselves ''en 

 presence d'un assez grand nombre d'images d'un aspect nouveau, 

 parfois tres inattendu ou meme deconcertant" (op. cit., p. 90). 

 Further work on this genus seemed to be warranted by the very 

 peculiar appearances described by these authors, as well as by 

 the acknowledged slight treatment of the maturation divisions in 

 favor of the stages concerning the transformation into the sper- 

 matozoon. The problem was suggested to me by Prof. E. B. 

 Wilson, to whom I wish to express my most sincere thanks for 

 his valuable advice and criticism during the course of the investi- 

 gation. This study is based on the three common American 

 species, kindly identified by Mr. E. P. Van Duzee as -Notonecta 

 undulata (Say), N. insulata (Kirby) and N. irrorata (Uhler); 

 the form used by the French authors was the European species, 

 N, glauca. While the American species agree with N. glauca 

 in presenting many very puzzling appearances, they differ from 

 it in several important respects and also differ considerably 

 among themselves. The two facts of main interest are, first, 

 the presence of a karyosphere or body in which the chromatin is 

 aggregated during the growth stages in all three species, as was 

 noted also in N. glauca by Pantel and Sinety; and secondly, 

 the relation of the chromosome number to the species, a brief 



