12 THOS. H. MONTGOMERY jr., 



the "12 dumbbell-shaped primary segments must therefore represent 

 single chromosomes, not bivalent ones, as Wilcox assumes". 



The following papers were inaccessible to me: Gilson ('85), 

 TicHOMiROFF ('91), ToYAMA ('94 b) and Wagner ('96). 



II. 

 Observations. 



A, The spermatogonia and their mitoses. 



The spermatogonia are the smallest cells in the testicle. Since 

 all of a given stage are not of exactly the same dimensions, it may 

 be concluded that the mature testicles which formed the basis of these 

 observations contained at least two generations of spermatogonia. 



There is one pair of testicles situated on the dorsal surface of 

 the body cavity, near the anterior end of the abdomen; they are 

 bright red in color, and thus may be clearly distinguished from the 

 other internal organs, which are of a light greenish color. Each 

 testicle is approximately oval and dorso-ventrally flattened, and is 

 composed of 6 follicles lying in one plane, all of which extend the whole 

 length of the organ (Fig. 227 represents a longitudinal section, and 

 Fig. 225, PL 5, a transverse section of the testicle). All the follicles 

 are not of the same diameter, and in those numbered 1 and 3 in the 

 figures, occurs the large generation of spermatocytes, which will be 

 described subsequently. Each follicle is bounded by a sheath of con- 

 nective tissue, formed of interlacing, branched connective tissue 

 cells, some of which also penetrate into the interior of the follicles. 



The branching processes of these connective tissue cells serve to 

 demarcate more or less spherical groups of cells, the spermatocysts 

 of V. LA Valette St. George (PL 5, Fig. 226), such spermatocysts 

 are found from the proximal end of the testicle to about the zone 

 where the spermatids occur (compare the explanation of Fig. 227). 

 In a given spermatocyst the cells are all approximately in the same 

 stage of development. In Pentatoma these spermatocysts are not so 

 well demarcated as those of e. g. the Salamander. How these cells 

 arise can be determined only by an examination of embryonal testes, 

 such as I have not had the opportunity to make. But it would a 

 priori seem probable that in the embryonic testis there would be a 

 network formed by the connective tissue cells, in each mesh of which 

 would lie a single spermatogonium, or at least only a small number 

 of spermatogonia. Then by the growth and repeated divisions of these 



