158 GRACE MEDES. 



they stain scarcely more densely than the linin and assume a 

 similar grayish appearance. 



OBSERVATIONS. 



Early in the spermatogonial stages, cells may be seen aggre- 

 gated in separate groups which are surrounded by definite mem- 

 branes, or cyst-walls (Fig. 3). The number of cells in these 

 groups varies considerably in those counted, from eight to 

 over a hundred. This may be due to either or both of two 

 causes. According to the general conception of a cyst, it is an 

 aggregation of cells consisting of all the descendants of one 

 primary spermatogonium. Observations supporting this theory 

 have been afforded by St. George, '76 (Rana tcinporana\ Henk- 

 ing, '91 (Pyrrhocoris aptcrus], Toyama, '94 (Bombyx\ Mont- 

 gomery, '98 (Pentatoma), Paulmier, '99 (Auasa], McGregor, '99 

 (Ampkiuma) t and Sutton, 'oo (Brachystold]. However, from 

 observations upon later stages, it is evident that in Scutigera 

 these cysts are not such permanent structures. By a series of 

 careful counts taken during the spermatogonial and early sper- 

 matocytic stages, it has been found that the number of cells in 

 cysts in the same stage of development exhibits considerable vari- 

 ation. The counts of early spermatocytes shows them to exist 

 in groups of from twenty-eight to forty. In the spermatogonia 

 the results were somewhat different. In these, the highest num- 

 ber of cells found in one cyst was one hundred and eight, while 

 the average number in cysts supposed to contain cells in the last 

 spermatogonial division was about sixty. This, to my mind, 

 can be due to but one cause : The cysts are not definite struc- 

 tures, but either by fusion cysts containing a larger number of 

 cells are formed, or, by the division of one, two cysts containing 

 a reduced number are produced. Sutton, in his paper on Brachy- 

 stola, has estimated that the number of cells in one cyst at the 

 close of the division period is two hundred and fifty six. In 

 this case, all of the descendants of one primary spermatogonium 

 are contained within one cyst, but in Scutigera, either this is not 

 the case, or the descendants of one of th^se primary spermato- 

 gonia are much fewer in number. That the former is true rather 

 than the latter, is indicated by the fact that in those cysts con- 



