470 Alice M. Boring 



INTRODUCTION 



The purpose of this investigation is to extend, to some famiUes 

 of the Hemiptera Homoptera, the studies of McClung, Stevens, 

 Wilson and others on the relation of the accessory or odd chromo- 

 some to sex determination. Except for the aphids, w^hich have 

 been extensively worked out by Stevens ('05a, '06a), Cicada tibi- 

 cens (Wilcox '95) and Aphrophora quadrangularis (Stevens '06b) 

 are the only species of this group whose spermatogenesis has been 

 previously described. This study covers eight species of the 

 Membracidae, six of the Jassidae, four of the Cercopidas and four 

 of the Fulgoridae. 



My work was begun at the suggestion of Dr. N. M. Stevens at 

 Woods Hole in the summer of 1905, continued under Prof. E. G. 

 Conklin, at the University of Pennsylvania, in the year 1905-06, 

 and completed under Dr. Stevens, at Bryn Mawr College, in the 

 year 1906-07. To both Dr. Stevens and Professor Conklin I 

 wish to express my appreciation of their valuable suggestions and 

 constant help and inspiration. I wish also to thank Dr. Herbert 

 Osborn of Columbus, Ohio; Mr. E. P. Van Duzee, of Buffalo; 

 Mr. H. C. Barber, of New York City, and Dr. H. Skmner, of 

 Philadelphia, for the identification of material. 



HISTORICAL REVIEW 



Most of the work on the spermatogenesis of the tracheate arthro- 

 pods has been done since 1890. Such studies as those of Biitschli 

 ('71), La Valette St. George ('85), Platner ('86), Verson ('89), 

 and Sabatier ('85) were concerned only with the formation of the 

 spermatozoa, the arrangement of the cells of the testis into cysts, 

 and the general mechanics of karyokinesis. The work of van 

 Beneden ('84), Boveri ('87) and O. Hertwig ('90) on Ascaris, 

 and Mark ('81) on Limax, turned the interest in the study of the 

 sex cells to the chromosomes, while Weismann's daring hypothesis 

 ('87) as to equational and reducing divisions added to the interest. 

 By 1890, practically all investigations on spermatogenesis centered 

 around the chromosomes in the spermatocyte divisions, and in 



