186 W. E. AGAR 



able to assume that this represents the point of attachment of 

 the X-chromosome. 



As will be described in more detail below, similar conditions 

 are found in the meiotic division. The XY bivalent is possibly 

 sometimes independent, but more often it is attached to one 

 of the autosomes. In this phase, however, the XY is easily 

 identifiable even when attached to an autosome. 



In the fact of its usual attachment to an autosome but 

 occasional independence, both in spermatogonial and meiotic 

 mitoses, the X-chromosome in Ma crop us resembles that 

 of Ascaris megalocephala (Edwards, 1910). In many 

 male Orthoptera also the X-chromosome is temporarily or 

 permanently united to an autosome (McClung, 1905 ; Wilson, 

 1911). 



In the female (Graafian follicle cells) the small Y-chromosome, 

 so characteristic of the spermatogonia, is not present. I have 

 never been able to find more than ten separate chromosomes, 

 and here, as in the male, the small number of chromosomes 

 makes it easy to find a large numl^er of dividing nuclei in 

 which every chromosome is distinct (PI. 12, figs. 4, 5). Since 

 there is no Y, and since in the male, X is generally attached to 

 an autosome, it is quite safe to interpret the ten chromosomes 

 of the female as 10 + XX, and the two X's attached to auto- 

 somes. The condition here is again comparable to that found 

 in A . megalocephala, where Frolowa (1912) found that 

 the two X-chromosomes are generally attached to autosomes 

 in the female. 



The Meiotic Phase . — The spermatogonial nuclei (PI. 1 2, 

 fig. 1) contain a very scanty chromatic reticulum and a large 

 central nucleolus. This is apparently a plasmosome impregnated 

 with chromatin, for it stains densely with iron haematoxylin, 

 but in well-balanced methyl green and acid fuchsin preparations 

 it takes up the fuchsin. In the early prophase of the spermato- 

 gonial mitoses this nucleolus loses its chromatic staining 

 reaction even with iron haematoxylin, and becomes a typical 

 plasmosome. This nucleolus is the onh^ compact body in the 

 resting spermatogonial nucleus, so unless they are somehow 



