ODONTOTA DOESAUS. 39 



history it stains like dense chromatin, and my only suggestion as to its 

 origin is that it seems, from a study of this and other species of beetles, 

 to be a derivative of the chromatin of the spermatid, increasing in size 

 for a time, then decreasing, and finally breaking up into granules and 

 dissolving in the'karyolymph. Whether it has any function connected 

 with the development of the spermatozoon, or whether it is merely 

 material rejected from the chromosomes, as in many cases in oogen- 

 esis, one can only surmise. 



In one testis a peculiar abnormality was found. In all of the perfect 

 spermatogonial plates two small chromosomes were present (figs. 89, 

 90). Nineteen such plates were counted in five difi'erent cysts. All 

 of the equatorial plates of the first spermatocytes showed 8 chro- 

 mosomes, as usual. In a few favorable growth stages (fig. 91) the 

 two small chromosomes were seen to be combined with the larger 

 heterochromosome and a plasmosome, and one first spermatocyte 

 spindle was found in which the same combination could be clearly 

 seen (fig. 92). All of the second spermatocyte metaphases in which 

 a small chromosome occurred, contained two small ones, making 9 in 

 all (fig. 93). The others contained 8 large chromosomes, as usual. 

 The only explanation suggested by the conditions is that somewhere 

 in its history, the small chromosome had undergone an extra division, 

 and that ever afterward the two products behaved like the one small 

 heterochromosome of a normal individual. The chief interest in this 

 abnormality centers in the fact that the two small chromosomes of 

 this specimen behave exactly like the usual single one, emphasizing 

 the individuality of this particular heterochromosome. Both evidently 

 have the same individual characteristics and affinities as the one in 

 other cases. 



Epilachna borealis (Family Coccinellidae). 



Epilachna borealis was found in abundance on squash vines at 

 Woods Hole, Massachusetts, in September. The testes, unlike 

 those of most of the Coleoptera, consist of many free follicles similar 

 to those of the Orthoptera. The germ glands were rather far 

 advanced, but some good spermatogonial and spermatocyte cysts 

 were found. In figure 94, a spermatogonial metaphase, the small 

 chromosome is shown with 17 larger ones. The heterochromosome 

 pair appears in condensed form in the spireme stage (fig. 95), and again 

 in the first maturation spindle (figs. 96, 97). The varying forms of 

 the ordinary chromosomes are shown in figure 98. Figures 99 and 

 100 are equatorial plates of the first mitosis. The unequal pair is 

 shown by itself in figure loi, and the separation of the heterochromo- 



