BLEPHARIDA RHOIS. 4 1 



Blepharida rhois (Family Chrysomelidae). 



The testes were rather too far advanced when this material was 

 collected and no dividing spermatogonia were present. The growth 

 stages (figs. 131, 132) show a faintly staining spireme and a hetero- 

 chromosome group similar to that of Odontota, a large and a small 

 chromosome attached to a large plasmosome. The spireme appears 

 to go directly over by condensation and segmentation into the dumb- 

 bell-shaped figures seen in the first maturation spindle (figs. 133, 134), 

 though cross-shaped bivalents occasionally occur (fig. 135). The 

 heterochromosome pair, slightly separated by plasmosome material, is 

 usually found at the periphery of the plate (figs. 133-136). Figure 



137 is an exceptional anaphase in which the heterochromosome 

 elements are not mingled with the polar masses of chromatin. Figures 



138 a and b are equatorial plates of the second mitosis, and figures 139 

 and 140 are pairs of daughter plates from second spermatocytes show- 

 ing again the dimorphism of the spermatozoa as to their chromatin 

 content. As in several of the forms studied, material was collected for 

 examination of the somatic cells, but no favorable cases of mitosis were 

 to be found. 



Silpha americana (Family Silphidae). 



Only one male of this species was secured, but the large testes gave 

 all stages in abundance. The chromosomes, however, were very 

 small and too numerous, 40 in the spermatogonia (fig. 141). The 

 small chromosome is, nevertheless clearly distinguished in many of 

 these plates (s). The resting spermatogonium contains one very large 

 plasmosome and often one or two smaller ones (fig. 142,/). The 

 unequal pair is seen in the growth stages (figs. 143, 144), and may 

 frequently be seen outside of the equatorial plate of the first sperma- 

 tocyte spindle (fig. 146). In favorable sections it may also be found 

 in the plate among the other bivalents (fig. 147). Figure 145 is a 

 prophase showing the bivalent chromosomes still connected by linin 

 fibers. An equatorial plate of the first division is shown in figure 

 148, and a pair of corresponding plates of the second spermatocyte in 

 figure 149. The small heterochromosome divides in the second spindle 

 in advance of the others as seen in figure 150. Therefore, although 

 this form is not especially favorable for detailed study on account of 

 the large number of small chromosomes, the conditions are evidently 

 the same as in the other species described — an unsymmetrical hetero- 

 chromosome bivalent in the first spermatocyte, giving rise by the 

 second maturation division to equal numbers of dimorphic sperma- 

 tozoa, one class receiving the large heterochromosome, the other class 

 the small one. 



