122 WILLIAM M. GOLDSMITH. 



tinction between the various kinds of nucleoli. This difficulty 

 renders it almost impossible to present a satisfactory review of 

 the literature of the plasmosome, as so many writers discuss the 

 "nucleoli" when even the context fails to indicate the kind of 

 nucleoli under consideration. Carnoy ('85) finds four distinct 

 kinds, namely, "nucleoles nucleiniens, nucleoles plasmatiques, 

 nucleoles mixtes, and nucleoles noyaux." It seems advisable, 

 however, to adhere closely to the well-known broader classifica- 

 tion (chromatic and achromatic nucleoli) and always endeavor 

 to make the distinction very clear. 



OBSERVATIONS. 1 



It would be very desirable to have at hand a large number of 

 species which show the points under consideration. As this is 

 impossible at this time, I shall present the results based upon a 

 study of Psettiodes (milyas) cinctus Fabr. 



The testes of Pselliodes cinctus are composed of cylindrical 

 but tapering follicles which are wound about in a very irregular 

 form. Each follicle contains definite walled cysts, but on account 

 of this winding shape it is very unusual to obtain even a longi- 

 tudinal section which shows more than a half dozen cysts in the 

 same follicle. This difficulty, however, is offset by the fact that 

 the follicles show a regularity in the zonation of the various 

 stages of development from one end to the other. Even though 

 many stages of growth may be omitted, no cyst has been found 

 containing cells which are in a more advanced stage than those 

 further down the follicle. This makes it a comparatively easy 

 matter to obtain the sequence of stages in development. 



Since it is primarily beyond the scope of this paper to deal 

 with the chromatic parts of the cell, except so far as related 

 directly to the development of the achromatic parts of the 

 nucleolus, the figures include only the stages of the growth period 

 between the synaptic stage and the first spermatocyte division. 

 Incidentally, however, observations were made upon the stages 

 of spermatogenesis both preceding the appearance and following 

 the disappearance of the plasmosome material. The periods in 



1 While working on the sex-chromosomes in the Reduviidae, Dr. F. Payne made 

 observations which enabled him to suggest the present line of research. 



