SPERMATOGENESIS 



21 



FIG. 16. DORSAL (a) AND 

 LATERAL (b) VIEWS 

 OF THE ABDOMEN OF 

 GRASSHOPPERS. (After 

 Hyatt and Scudder.) 



SPERMATOGENESIS. 



In its essential features, the process of spermatogenesis in insects 

 corresponds with that in mammals, and very favorable material can be 

 obtained in abundance from grasshoppers of various 

 genera. 



The males may be distinguished from the females by the 



shape of the abdomen. In males it is more rounded (Fig. 16) 



with various appendages directed dorsally. The abdomen 



of the female is pointed, terminating in the ovipositor, the 



parts of which as seen from the side may be together, or 



widely separated dorso-ventrally. The genital glands can be 



readily removed by dissecting as follows: Male grasshoppers, 



which have been chloroformed, are opened by a mid-ventral 



incision. The abdominal walls are pinned out on a wax plate 



under normal salt solution (0.6 per cent.). The intestinal 



tube, which is usually black or green, is taken out with forceps, 



and the yellow or orange testes are seen close together at the 



upper end of the abdomen, attached to the back. Each testis 



consists of a number of separate cylindrical lobes, and it should 



be worked loose from the surrounding tissue with forceps in 

 such a way that these lobes remain together. The tissue 

 may be preserved in Flemming's strong solution or in Her- 

 mann's fluid, and stained with iron haematoxylin. 



Among the many publications upon spermatogenesis 

 in the grasshoppers, the following may be cited: McClung, 

 C. E., The accessory chromosome sex determinant? Biol. 

 Bull., 1902, vol. 3, pp. 43-84; Button, W. S., On the mor- 

 phology of the chromosome group in Brachystola magna, Biol. 

 Bull., 1902, vol. 4, pp. 24-39; McClung, C. E., The chromo- 

 some complex of orthopteran spermatocytes, Biol. Bull., 

 1905, vol. 9, pp. 304-340; Robertson, W. R. B., The chromo- 

 some complex of Syrbula admirabilis, Kansas Univ. Sci. Bull , 

 1908, vol. 4, pp. 273-305; Davis, H. S., Spermatogenesis in 

 Acrididae and Locustidae, Bull. Mus. Comp. Zool., 1908, vol. 

 53, pp. 57-157; Wilson, E. B., The sex chromosomes, Arch, 

 fur mikr. Anat., 1911, vol. 77, pp. 249-371. 



/ As seen in sections, each lobe of the testis of the 



grasshopper contains a considerable number of closed 

 sacs or cysts, which are filled with sexual cells; and 

 all the cells within a cyst are in approximately the 

 same stage of development. The cysts are shown 

 in Fig. 17, which represents a longitudinal section 

 of a single lobe. Usually the testis is sectioned as a 

 whole, and the specimen consists of a group of lobes 

 cut transversely or obliquely. Cross sections from the apical portion , 

 furthest from the outlet, will contain younger stages than the sections 



d 



FIG. 17. LOBE OF THE 

 TESTIS OF A GRASS- 

 HOPPER. Xso. (After 

 Davis.) 



a, apical cell. 



b, spermatogonia. 



c, spermatocytes. 



d, spermatocytes dividing. 



e, spermatids. 



f, spermatozoa. 



