612 NATHAN FASTEN 



They appear completely fused and twice the size of the spennato- 

 gonial chromosomes. A polar view of the chromosomes in Cam- 

 barus virilis reveals 100 chromosomes, this being the reduced 

 number (figs. 28-29). In Cambarus inamunis, there are 104 

 chromosomes, seeming to be composed of 96 ordinary chromo- 

 somes and a peculiar group of eight, sometimes enclosed within 

 a clear vacuole (figs. 38 and 40). The chromosomes were out- 

 lined in the most careful manner by the aid of the camera lucida 

 and then the counts were made. 



During the reduction division, the chromatoid bodies in 

 Cambarus virilis may behave in either of the following two ways : 



1. They may both pass to one pole of the spindle. This is 

 the usual and common method of their behavior. In this case 

 the secondary spermatocytes produced differ from each other 

 in that one contains the two chromatoid bodies, the other being 

 without them (figs. 24-26, 30-32, and 85-90). 



2. One chromatoid body may pass to one pole of the spindle, 

 while the other passes to the opposite pole. This mode of be- 

 havior is the rarer of the two. Here the secondary spermato- 

 cytes produced each contain one chromatoid body (figs. 33-35 

 and 91-93). 



There are thus produced three types of secondary spermato- 

 cytes: (1) Type A, containing two chromatoid bodies (fig. 32); 



(2) Type B, containing one chromatoid body (fig. 35) ; and 



(3) Type C, containing no chromatoid body (fig. 36). 



The chromatoid bodies lie outside of the spindle and long 

 before the autosomes have made their way from the equator of 

 the poles, these bodies are already seen to migrate towards them. 

 In many cases they are actually at the poles during the metaphase 

 stage (figs. 24-26, 30-35) and 85-93. Their position is outside 

 of the spindle and in the cytoplasm. This is especially seen in 

 ultimate telophase stages where the nuclear wall has already 

 formed around the chromosomes. In such stages the bodies 

 remain in the cytoplasm, as is shown in figures 31, 32, 35, 89, 90 

 and 93. 



In Cambarus immunis these bodies could not be studied, this 

 being due, in all probability, to the fixation of the material. 



