46 J. T. PATTERSON AND LELIA T. PORTER. 



After the division of the cytoplasm, the two spermatids remain 

 connected for some time by means of the interzonal fibers (Fig. 

 1 8). After they separate, each differentiates into a typical 

 spermatozoon (Figs. 19, 20). We shall not discuss further the 

 subject of the metamorphosis of the spermatids, except to em- 

 phasize the point that both spermatids must form functional 

 germ cells, as we have found no evidence of degenerating sperma- 

 tids or spermatozoa. 



COMPARISON WITH OTHER HYMENOPTERA. 



Studies on the spermatogenesis of Hymenoptera have shown 

 that there is a striking modification of the maturation process 

 in those species in which sex-determination is supposed to be 

 in accordance with the Dzierzon theory. Instead of four sperma- 

 tozoa arising from each first spermatocyte, only one or two 

 matured germ cells develop. In one group of these Hymenoptera 

 both spermatocyte divisions are abortive; the first division 

 cutting off a small cytoplasmic bud free of chromatin, and the 

 second division a small bud which receives half the chromatin. 

 There is thus produced but a single spermatid, and consequently 

 only one spermatozoon. In the second group the first division 

 is likewise abortive, producing a cytoplasmic bud, but the second 

 division is equal, producing two similar spermatids, which meta- 

 morphose into spermatozoa. 



To the first of these groups belongs the honey bee, as has 

 been shown by the work of Meves ('03, '07), Mark and Copeland 

 ('06), and Doncaster ('06, '07). To this class there also probably 

 belongs the solitary bee (Osmia cornuta) worked on by Arm- 

 bruster ('13). 



The second group includes a number of different species, of 

 which the following may be mentioned: Xylocopa violacea 

 (Granata, '10, '13), Neurotems lenticularis (Doncaster, '09), 

 Vespa crabro (Meves and Duesberg, '08), Vespa metadata (Mark 

 and Copeland, '07), Vespa germanica (Meves, '03), Camponotus 

 herculaneus (Meves and Duesberg, '08, and Lams, '08), Dryo- 

 plianta erinacei (Wieman, '15). Paracopidosomopsis floridanus 

 also clearly belongs to this class. , 



While the various investigators report differences as to details 



