614 NATHAN FASTEN 



(figs. 41-42), reveals that they are about half the size of the chro- 

 mosomes in the primary spermatocyte stage. They are more or 

 less round, condensed and distributed over the entire equatorial 

 plate. Numerous counts of these polar views revealed 100 

 chromosomes in Cambarus virilis (fig. 42) and 104 chromosomes 

 (including the clump of eight) in Cambarus immunis (fig. 41), 

 These counts were made after careful tracings with the camera 

 lucida. 



The three types of secondary spermatocytes produced artd 

 enumerated under our discussion of the primary spermatocyte 

 stage, behave in the following manner: 



Type A. When this form divides there are two possibilities: 

 (1) the two chromatoid bodies may migrate to one pole, pro- 

 ducing a spermatid with both these bodies, while the other is 

 without them (figs. 46-^0 and 94-100); or (2) one chromatoid 

 body may go to one pole and the other may go to the opposite 

 pole, giving spermatids containing one of these bodies each 

 (figs. 51-53 and 104-106), The first of these modes of behavior 

 is the most usual. 



Type B, In the division of this type, the one chromatoid 

 body goes to one pole, giving rise to a spermatid containing this 

 body and an other spermatid without it (figs. 54-56 and 101-103). 



Type C. The spermatids resulting from the division of this 

 form are all without either of the chromatoid bodies (figs. 43-45). 



In the anaphase stage the chromosomes divide equationally 

 and drift to opposite poles to form the telophase stage. During 

 the late telophase of this division, as* in the other divisions men- 

 tioned, a zwischenkorper is formed in the center of the spindle 

 (fig. 44) . After the cells become constricted from each other, this 

 body remains outside of the cells and soon disintegrates. In 

 this stage, as in the primary spermatocyte division, the chro- 

 matoid bodies lie in the cytoplasm outside of the spindle as can 

 be seen in the drawings and in the photographs. Thus three 

 types of spermatids are produced, namely: 



(1) Type A', containing two chromatoid elements (figs. 50, 

 99 and 100). 



