(lO 



bulletin: museum of comparative zoology. 



4. The maturation di- 

 visions 127 



5. The allosomes . . 133 



6. The individuality of 



the chromosomes . 140 





7. The metamorpho.sis 



of the spermatid . 143 



V. Summary 145 



BibHography 148 



Explanation of plates . . 159 



I. Introduction. 



The investigations which form the basis of this paper were begun in 

 the Zoological Laboratory of Harvard University during the winter 

 of 1900-1901. They were continued at irregular intervals in con- 

 nection with the author's work at the Washington State College, Pull- 

 man, Wash., and have been brought to completion during the present 

 year (1906-1907) in the Zoological Laboratory of Harvard University. 

 However, most of the observations can be considered as made during 

 the present year since, in addition to much new material studied, the 

 previous work has been gone over anew and most of the figures re- 

 drawn. My warmest thanks are due to Prof. E. L. Mark, under 

 whose direction this work has been done and to whom I am indebted 

 for many helpful suggestions and criticisms. 



Considerable work has been done upon the spermatogenesis of the 

 Orthoptera but with remarkably diverse results. There is probably 

 no other group in which such radically opposed conclusions have been 

 reached by dift'erent investigators. Just why this is so, it is hard to 

 say. The material is in general very favorable for cytological work, 

 since the cells and chromosomes are large, and in many species ex- 

 hibit remarkably clear structures. 



Carnoy ('85) was the first to describe and figure the divisions of the 

 male germ cells of Orthoptera. Von La Valette St. George ('86) 

 described the spermatocyte divisions and the metamorphosis of the 

 spermatid in Blatta. Vom Rath ('92, '95) found that in the spermato- 

 genesis of the mole cricket (Gryllotalpa) the first maturation division 

 was longitudinal, the second transverse, or in other words a reduction 

 division. On the other hand, Wilcox ('95, '96), working on Calop- 

 tenus (Melanoplus, an acridid), arrived at very dift'erent conclusions, 

 holding that in this species both maturation divisions are transverse. 

 Wilcox also gave a detailed account of the metamorphosis of the 

 spermatid. La 1899 McClung in a short paper called attention to the 

 existence in the male germ cells of Xiphidium of a peculiar chromo- 

 some, characterized by remaining compact and staining deeply during 

 the resting stage of the primary spermatocyte. This element he called 



