92 E. L. SHAFFER. 



out, he has confined his idea of this similarity of chromosome 

 number in closely related species, only to the family Acrididse. 

 It is possible that in other forms correspondence in chromosomes 

 may extend only to the subfamily or genus. In the Hemiptera 

 and Coleoptera certainly there is no such uniformity of chrom- 

 osome number in the various families as is found in the Acrididse. 

 The four species of Lachnosterna studied here differ from each 

 other very much as far as taxonomic characters are concerned, 

 nevertheless the chromosome groups show no difference either 

 in form or number. The two other forms studied, Pelidonota 

 and Cotalpa, differing generically, have the same chromosome 

 number (20 in the diploid groups), but there are some differences 

 in the form of the maturation tetrads. Only one other scarab 

 bettle has been studied, Euphoria inda by Stevens ('06), and it 

 corresponds with a diploid group of 20 chromosomes, so that all 

 the species of the family Scarabidce thus far studied correspond 

 in chromosome number. The genus Lachnosterna embraces 

 over one hundred species, some very much alike so that it is 

 difficult to separate them taxonomically, others differing markedly 

 from each other. The most constant difference is found in the 

 male copulatory organs, which probably prevents the inter- 

 breeding of species in nature. Perhaps further cytological 

 studies in this genus will yield results similar to those in the 

 Acrididse. Certainly there is a wealth of material for such a 

 comparative study. 



2. Cyst Formation and Cell Polarity. 



Hegner ('14) has studied the formation of spermatogonial 

 cysts in the testes of Leptinotarsa; the facts concerning cyst 

 formation in the beetles studied here show results essentially 

 similar to those of Hegner. The primary spermatogonia are 

 not arranged in cysts and are more or less polygonal in shape, 

 with the nucleus usually located in the center. Cyst formation 

 begins by the rapid division of a single primary spermatogonium, 

 together with an adjacent epithelial cell which forms a follicular 

 membrane around the cyst. Consequently we can say that all 

 the cells within any one cyst are the descendants of a single 

 primary spermatogonium. With the formation of the cyst, 



