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function, might throw light on the chromatin substance and its bearing 

 on heredity seemed more probable than ever before, e^pe<'ially if it 

 could be shown that this held true for all classes of animals. In sum- 

 marizing the work on this subject, McClung (1902) says the accessory 

 chromosome has been found in all insects so far studied, is present in 

 different members of Orthoptera, and, in examining material from 

 Hemiptera, Neuroptera, Coleoptera, and Lepidoptera, this body was 

 found. Miss Wallace has found it in Arachnida and the probability of 

 its general occurrence in Arthropods is thus largely increased. Some 

 hurried examination of vertebrate spermatocytes lead McClung to 

 believe that the accessory chromosome is likewise present among ver- 

 tebrates and that it will probably be found to be universal. 



Except this reference of McClung's to the accessory in Lepidoptera, 

 no other mention of it was found ; and, since no recent detailed exam- 

 ination of the spermatogenesis of Lepidoptera had been undertaken, it 

 seemed advisable to examine members of this group. Accordingly, in 

 September, 1905, at Dr: Conklin's suggestion, I began to collect material 

 with the purpose of studying the accessory chromosome in Lepidoptera. 

 Testes were fixed and cut from a number of genera and species, but in 

 most cases were found unsatisfactory. Philosamia cyntltia was partic- 

 ularly clear and was chosen as a basis for comparative work. Owing 

 to the publication of Dederer (1907) on this species, I shall refer to my 

 own work only when my results differ from hers. 



This paper contains, aside from references to Philosamia cynthia, a 

 study of the spermatogenesis of CaUosamia promethea, Telea polyphemus, 

 Automeris to, Samia cecropia, and Acronycta (sp. ?) as well as a few com- 

 parisons with Danais archippus and Papilio cresphontes. I am indebted 

 to Prof. Calvert, of the University of Pennsylvania, and to Dr. Skinner, 

 of the Academy of Natural Sciences, for aid in the identification of 

 the species here described. The work was done in the Biological 

 Laboratory of the University of Pennsylvania under the direction of 

 Prof. Edwin G. Conklin. I am glad of this opportunity to express my 

 feeling of gratitude to Prof. Conklin for his help and encouragement 

 throughout the years of my work as well as for his suggestions and for 

 criticisms of this paper. 



I. Previous Work. 



The published works upon Spermatogenesis in Lepidoptera may be 

 divided into two classes: the earlier works, including those of Carnoy 

 (1884), Platner (1889), Cholodkovsky (1894), Verson (1894), Erlanger 

 (1896), La ValetteSt. George (1897), Henneguy (1891), Meves (1890), 



