60 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
4. The maturation di- | 7. The metamorphosis 
visions’ [01a POMeTA of the spermatid . 143 
5. The allosomes. «>... Lod eV a soummary .). 2 i, Tee 
6. The individuality of Bibliooraphy ©... 0 >: eee 
the chromosomes . 140 | Explanation of plates . . 159 
I. Introduction. 
‘The investigations which form the basis of this paper were begun in 
the Zodlogical 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. EK. 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. ‘here is probably 
no other group in which such radically opposed conclusions have been 
reached by different 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 different conclusions, 
holding that in this species both maturation divisions are transverse. 
Wilcox also gave a detailed account of the metamorphosis of the 
spermatid. In 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 
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