416 Sidney I. Koinhauser 



were in coiitact (Fig. 6^3), and through further condensation the type 

 in Figure G 4: would be reaclied. 



Figures 24 a— ö, and 26 a— & picture two spermatocytes before the 

 formation of the spindle. The former is unusual, for at this stage seldom 

 more than two ring tetrads are to be found in the nucleus. The cell 

 sho^^Ti in Figures 26 a— & is slightly more advanced than that in Figures 24 

 a—h. The chromosomes are fully Condensed and show neither the longi- 

 tudinal division nor the "Querkerbe"; the cell membrane is no longer 

 present, and the nucleolus has entirely disappeared; the "nuclear cap" 

 is contracted or diminished in size to a small sphere, which shows a light 

 staining center, as if it were liollow. 



A count of the chromosomes in this cell shows that thii'teen are 

 present. In as much as the normal number of chromosomes in the sper- 

 matogonia is twenty-four and the primary oöcytes (Fig. 49, Plate VI) 

 aU have twelve chromosomes, it is puzzling to understand why there 

 should be thirteen here. This is, however, explained by the maturation 

 divisions which show that in the male there is a peculiar pair of chromo- 

 somes which do not behave like the autosomes. 



B. Oöcytes. 



The seriation of the stages in the oögenesis has been described in 

 considering the structure of the ovary, and the minute details in the 

 formation of the leptotene threads and the conjugation will be omitted, 

 as it would be but a repitition of what occurs in the spermatocytes. 

 Figures 45—47 (Plate VI) demoustrate the similarities and differences 

 in the two sexes. The leptotene tlu'eads (Fig. 45) never assume the 

 orderly arrangement toward the positive pole to the same degree as 

 that found in the spermatocytes (Fig. 12 e). Thus the threads present 

 a far more scattered and confused appearance, a condition which is also 

 characteristic of the ceUs showing conjugation (Fig. 46); and on account 

 this less orderly arrangement of the threads and the larger size of the of 

 nucleus, the conjugants can be more easily seen and foUowed. In the 

 middle of Figure 46, one sees a pair of threads which have conjugated 

 along the middle but which are still separate at both ends; at the left 

 is a pair which have begun the process of conjugation from one end. In 

 this nucleus, besides the conjugants, there are completed 'double threads 

 and wholly nnconjugated leptotene threads, — indicating a progressive 

 Union. That the process is a progressive one is proved by the stages 

 immediately following, in which all the threads are double. Concomitant 

 with the conjugation of the leptotene threads are the union of the cyto- 



