SPERMATOGENESIS OF STENOBOTHRUS VIEIDULUS. 19 



Wilcox, E. V. 



1806. Further Studies on the Spermatogenesis of Calo^ytemis femur-rubrum. Bull. 

 Mus. Comp. Zool, Harvard, vol. xxx. 

 Wilson, E. B. 



1905. The Chromosomes in Relation to the Determination of Sex in Insects. Science, 



vol. xxii. 

 Studies in Chromosomes. Jomui. Exp. Zool. vol. ii. 



1906. Ditto. Journ. Exp. Zool. vol. iii. 



1907. The Case of Anasa tristis. Science, vol. xxv. 



A fuller and very complete list is given by Henderson at the end of his 

 paper upon the spermatogenesis of Dytiscus marginaUs, Zeitschr, f. wiss. 

 Zool., Bd. Ixxxvii. 1907. 



The Zoological Laboratories, 



Victoria University, Manchester. 

 October 1910. 



EXPLANATION OF THE PLATES. 



The original drawings were made with the aid of a large Abbe camera lucida, and are 

 reproduced here at the same magnification. All the figures are magnified 2500 diameters, 

 except figs. 1 and 2, which are magnified only 750 diameters. The preparations were 

 studied by means of a Zeiss apochromatic oil-immersion objective of 2 mm. focus and 

 N.A. I'SO, and compensating oculars Nos. 6, 12, and 18. Illumination was obtained from 

 an acetylene burner, the light being directed on to the mirror through a globe condenser 

 containing a weak aqueous solution of copper acetate. 



All the drawings shown are made from preparations fixed with Perenyi's fluid and 

 stained with Heidenhain's iron hsematoxylin, and in certain cases counterstained with eosin. 

 The sections were cut to a thickness of 10 /i. I have endeavoured to render comparison 

 between the successive stages easy by adopting this plan of drawing the figures to the same 

 magnification. 



Plate 1. 



Fig. 1, Cyst containing apical cell surrounded by a single layer of primary spermatogonial 

 cells. The lobulate appearance of the distally placed nuclei of the latter is very 

 noticeable. The apical cell's nucleus exhibits the irregular masses of chromatin 

 and the peculiar cluster of deeply staining granules. 



Fig. 2. Cyst containing a cluster of secondary spermatogonia, and recognizable by the 

 •..b^ence of the apical cell. 



Fig. 3. Secondary spermatogonial metaphase, seen from one pole. The seventeen chromo- 

 somes are paired, and can be divided into three groups as regards size. The 

 heterotropic chromosome is the fourth largest, and is marked X. 



Fig. 4. Ditto. 



Fig. 5. Ijateral view of secondary spermatogonia! telophase. The heterotropic chromo- 

 some has divided late. 



Fig. 6. Eesting- or growth-stage immediately following secondary spermatogonial mitosis. 

 The ordinary chromosomes have become resolved into an apparent reticulum, in 



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