16 BULLETIN : MUSEUM OF COMPA1UTIVE ZOOLOGY. 



217, 229, 413, 418), Stuhlmann ('8G, Figs. 228, 233), and Moore 

 ('93, Fig. 1). 



The terminology which I have used is that of La Valette St. George, 

 as adapted by Boveri : — 



Spermatogonium = Hertwig's Ursamenzelle. 



Spermatocyte, 1st order = " Samenmutterzelle. 



Spermatocyte, 2d order = " Samentochterzelle. 



Spermatid = " Samenenkelzelle. 



Spermatozoon. 



G. W. Field ('93) uses a terminology which seems to admit one less 

 spermatocyte stage than is recognized by authors generally : " We find 

 that the largest cells, the spermatogones (using the nomenclature pro- 

 posed by La Valette St. George and now very generally adopted), 

 divide by mitosis and form two spermatocytes. Next each spermato- 

 cyte divides, also by mitosis, forming two spermatids. Each spermatid 

 then changes directly into the spermatozoon, without further division. 

 Thus each spermatogone gives rise to four spermatids." Field uses this 

 apparently as a general scheme of spermatogenesis. " Spermatogones " 

 are, I suppose, spermatogonia. But they are not " the largest cells " in 

 Boveri's scheme, nor do I find that La Valette St. George or any other 

 author has applied the term to these large cells, which Boveri desig- 

 nates as spermatocytes of the first order. The spermatogonia after they 

 have ceased dividing as spermatogonia become by a process of growth 

 spermatocytes (Bovei'i's spermatocytes, 1st order). Field's "sperma- 

 togones" therefore probably correspond to Boveri's spermatocytes of 

 the 1st order, his " spermatocytes " to Boveri's spermatocytes of the 

 2d order, and the spermatogonia of Boveri are unmentioned. Field has 

 therefore extended the use of the term spermatogonia to cover the whole 

 period of that cell generation which Boveri calls at its beginning the last 

 generation of spermatogonia, and during the rest of its existence sper- 

 matocytes of the first order ; consequently he designates as a spermato- 

 gonium division one that Boveri calls a spermatocyte division. It is 

 difficult to see why the fact that " each spermatocyte divides also by 

 mitosis" need be so strongly emphasized. It would be much more 

 strange if the spermatocytes divided amitotically (compare vom Rath 

 '91 and '93, and Ziegler '91). 



Henking ('91) in his paper on Pyrrhocoris has considered the origin 

 and fate of the chromatic rings. His Figures 13-20 show stages in the 

 formation of the rings. Henking differs from most other authors in 

 denying that there is any doubling of the chromosomes between the last 



