PLATE 3 



EXPLANATION OF FIGURES 



16 Spermatogonia! complex in metaphase. A, A, the largest pair of chromo- 

 somes. This figure represents the full number in the complex — 37. From a 7-day 

 old rat. X 4200. 



17 Division of spermatogonial chromosomes. Only a few of the chromo- 

 somes are shown, some in lateral and some at end view. From same rat as figure 

 16. X 4200. 



18 to 20 Polar views of first spermatocyte complexes. The letters, A, B, C, D 

 designate particular chromosomes; A', the accessory; Crt., the chromatoid body; 

 Nn., nucleolus or plasmosome. Chromosomes drawn with dotted lines in figure 

 18 are those whose detailed structure could not be determined. C(?) is either a 

 ring or a cross, probably a ring. In figure 19, the large, irregular chromosome in 

 the center, just above D, seems to be a cross. Figure 19 is from a smear; the other 

 two from sections. Figure 20 is from a testis fixed in Flemming's fluid. X 4200. 



21 Early anaphase from a poorly fixed first spermatocyte (the only figure 

 taken from this animal). The chromatin is badly clumped, but the different 

 divisions determinable are indicated. It is introduced to show the accessory 

 passing undivided in the first spermatocyte division. X 4200. 



22 Late anaphase from a well-fixed first spermatocyte. Accessory (A') at 

 only one pole. One large chromosome appears not yet fully divided; some simple 

 V's are also evident. X 4200. 



23 Second spermatocyte; some of the chromosomes in early anaphase. 

 X 4200. 



24 Second spermatocyte ; some of the chromosomes in late anaphase. X 4200. 



25 and 26 Two stages in interkinesis. Figures in each case show only a part 

 of the total number of chromosomes present. X 4200. 



ISO 



