STUDIES ON INSECT SPERM ATOGENESIS. 319 



arbitrary steps or stages, based for the most part upon the con- 

 dition of the chromatin in the nucleus. In the case of the He- 

 miptera the nuclear changes have been studied with exceptional 

 thoroughness particularly by Wilson and Montgomery, and the 

 steps from spermatogonium up to a late period in sperm forma- 

 tion are completely determined. I will, therefore/ make use of 

 the descriptive terms employed by Wilson ('12) in his outline oi 

 the stages, since they furnish well known landmarks and more- 

 over designate periods of profound nuclear changes which, it is 

 interesting to note, are accompanied by simultaneous changes in 

 the cytoplasm. 



(a) Polymegalous Spermatocytes and Sperms in the Family 



Pcntatomidcu. 



Hemiptera of the Family Pentatomidce possess two compact 

 testes, each enclosed in a delicate sheath of connective tissue, 

 which is continued into the body of the gland in the form of 

 septa or partitions dividing it into a number of compartments or 

 lobes. The latter are arranged parallel to the long axis of the 

 testis and vary in number (in the forms which I have examined) 

 from three to seven, the number being constant, however, for 

 any particular species. Speaking generally, the plan of the testis 

 is not unlike that of some other families of Hemiptera, but in its 

 details there is one notable difference in respect to which this par- 

 ticular family is unique, so far as known. I refer to the curious 

 fact, to which Montgomery ('98) first called attention, that in 

 Euschistus certain lobes of the testis are composed characteris- 

 tically of spermatocytes unusually large or unusually small ("di- 

 megaly") as contrasted to those of other lobes, which latter for 

 want of a better term might be called " normal " in size. Subse- 

 quently Montgomery ('10) published a much more complete 

 account of this unusual condition, establishing the fact that in 

 Euschistus sp., two of the lobes consist of unusually large sper- 

 matocytes, a single lobe of unusually small ones, while the re- 

 maining three lobes are normal. He found the spermatogonia 

 and early spermatocytes to be all of the same size, but that fol- 

 lowing the synaptic period the size differences are established by 

 differential growth. The relative differences he found to be 



