116 bulletin: MUSEUM OF COMPARATIVE ZOOLOGY. 



IV. Discussion. 



1. The Apical Cell. 



The apical cell is a large element of characteristic appearance. It 

 occurs at the distal ends of the follicles c^uite generally in the testes of 

 insects, and also, in some cases at least, in their ovaries. This cell 

 was formerly known as Verson's cell, after its supposed discoverer; 

 but, as Cholodkovsky (:05) points out, it was in reality first described 

 by Spichardt ('86). There would therefore seem to be no good reason 

 for retaining the name, and I have preferred to use the more appro- 

 priate term of apical cell given it by Griinberg (:03). 



The apical cell was first found and has been chiefly studied in the 

 Lepidoptera, where it is the most conspicuous element in the entire 

 testis. The following authors have described the apical cell in this 

 group of insects:— Spichardt ('86), Verson ('89, '91, '94), Cholodkovsky 

 ('94), Toyama ('94), La Valette St. George ('97), Tichomirow ('98), 

 Griinberg (:03), and Munson (:06). Toyama, La Valette St. George 

 and Griinberg also found a similar cell in the ovary. 



In Lepidoptera the apical cell, besides being much larger than the 

 other elements of the testis, has an irregular outhne. Near the center 

 of the cell is a large nucleus, while distributed through the cytoplasm, 

 especially in the vicinity of the nucleus, are large numbers of deeply 

 staining granules. The cell is closely surrounded on all sides by 

 several concentric layers of spermatogonia. 



Cholodkovsky ('92, '94, :05) has found the apical cell in the testes 

 of several Diptera, a hemipteron (Syromastes) and* a neuropteron 

 (Phryganea), while Holmgren (:01) has found it in a coleopteron 

 (Staphylinus). 



It seems not to have been previously reported for the Orthoptera, 

 although it was evidently seen by Sutton (:00), who supposed it to be 

 a degenerating spermatogonium which had become inclosed by the 

 fusion of two neighboring cysts. 



This cell seems to be of universal occurrence in the Acrididae and 

 Locustidae, as I have found it in a large number of species belonging 

 to both families. In no case have I failed to find the apical cell in the 

 usual position, although in some species it is much more conspicuous 

 than in others. I have also found a similar cell in the testes of a cricket 

 (Gryllidae) and a cockroach (Blattidae), so it probably occurs through- 

 out the Orthoptera. 



