Further Studies on the Chromosomes loj 



form often shows synapsis with unusual clearness (Fig. 55). Fig. 

 56 shows a late growth stage with the spireme still staining more 

 deeply than in most cases, and Fig. 57 the equatorial plate of the 

 first spermatocyte with twelve chromosomes. Metakinesis of 

 several of the bivalents and division of the centrosome are shown in 

 Fig. 58, and an early anaphase in Fig. 59. The second sperma- 

 tocytes contain eleven and twelve chromosomes (Fig. 60), as do 

 also the spermatids and spermatozoa. The sperm heads (Fig. 

 61) have a large middle piece which stains in iron haematoxylin, 

 but not in thionin. 



LISTOTROPHUS CINGULATUS (fAM. STAPHYLINID^) 

 STAPHYLINUS VIOLACEUS (fAM. STAPHYLINID^) 



Three rove-beetles have been examined with a rather small 

 amount of material in each case. All have an unequal pair of 

 heterochromosomes. Listotrophus cingulatus has twenty-six 

 chromosomes in the spermatogonia (Fig. 62), one being very small. 

 The heterochromosome pair is distinguishable in the synizesis 

 stage, which is of the spireme type, and in the later growth stages 

 both members of the pair are clearly separated and associated 

 with a large plasmosome. The chromosomes of the first sperma- 

 tocyte are shown in Figs. 63 and 64, and those of the second divi- 

 sion in Figs. 65 and 66. 



In the blue rove-beetle, Staphylinus violaceus, the heterochro- 

 mosome pair associated with a plasmosome is shown in Fig. 67. 

 The first spermatocyte contains twenty-two chromosomes (Fig. 

 68), and the unequal pair shows clearly in a section of a spindle 

 (Fig. 69). The two second spermatocyte equatorial plates appear 

 in Figs. 70 and 71. Another brown rove-beetle, not identified, 

 has twenty-eight chromosomes in the spermatogonia and fourteen 

 in the spermatocytes. 



TETRAOPES TETRAOPHTHALMUS (fAM. CERAMBYCID^) 

 CYLENE ROBINIA (fAM. CERAMBYCID^) 



Tetraopes, the common red milkweed beetle, has twenty chro- 

 mosomes. Two spermatogonial plates (Figs. 72 and y^) show 

 the different appearance of the chromosomes in different cysts. 



