pinney: chromosomes of anasa tristis. 357 



in numerous subsequent stages, for size comparisons. Fig. 14, 

 plate LXVI, shows several drawings from different individuals. 

 The spermatogonial cells from which drawings of the accessory 

 were made vary in age, and as there is undoubtedly a decrease 

 in the chromatin content of these nuclei as the cells multiply we 

 would naturally expect to find homologous chromosomes vary- 

 ing in size in the same individual. The position of the chromo- 

 somes with respect to the equatorial plane varies previous to 

 division, that is to say, in the formation of the equatorial plate 

 the chromosomes may lie obliquely to the plane of the equator, 

 and this would cause apparent differences in the size of camera 

 drawings. Conceding that these possible causes of size varia- 

 tion are sufficient to account for the slight variations in size 

 of the accessory as shown in the drawings, we are forced to con- 

 clude that the size of this element in the spermatogonia is 

 strikingly constant. A similar study of the homogeneous body 

 observed in the nucleus during synizesis shows a like con- 

 stancy in size. Although these two elements which appear at 

 different times in the nucleus are so unlike in form we cannot 

 but consider them as equal chromatin masses. Moreover, if 

 synapsis is a conjugation of twin chromosomes, obviously the 

 unpaired element of the earlier stages would take no part in 

 this process. This evidence is sufficient to incline us to believe 

 that the two masses are identical. Further evidence will be 

 given to strengthen this conclusion. An account of the presyn- 

 izetic stages or growth period will be given in the observations 

 on tlie first spermatocyte generation. 



The First Spermatocyte. 



The earliest condition of the spermatocyte cell is the result 

 of the disentanglement of the chromatin knot formed during 

 synizesis. Even before the chromatin has spread to the nuclear 

 membrane, and while the peripheral area is comparatively free 

 from it, it is easy to determine that the chromatin exists in the 

 form of granular threads or rods. See figures 1, 2, 3 and 4, 

 plate LXVI. This diffusion of the chromatin threads makes 

 possible the detection of a second body similar in size and 

 staining qualities to the chromatin body described as present 

 during synizesis. This body is not present before synizesis, is 

 not apparent during the synizetic period, and is present after- 

 ward in the interior of the nucleus. The natural conclusion 

 then is that this is a product of synizesis. Its staining qual- 



