48 MICHAEL F. GUYER 



field are for the most part characterized by their round, plump, 

 slightly eccentric nuclei with a comparatively large, well-marked 

 sphere of denser appearing cytoplasm at one side (fig. 10). In 

 places, however, they resemble closel}^ the spermatogonia lining 

 the inner wall of the tubules and, apart from location, are practi- 

 cally indistinguishable from them. Not infrequently, moreover, 

 scattered here and there among them are to be seen typical sper- 

 matocytes in process of division. Such areas appear to be the 

 remains of former tubules of which the walls have become entirely 

 obliterated and the characteristic arrangement of the tubule 

 cells lost. Such inter-tubular areas with numerous cells exhibit- 

 ing various features of the maturation phenomena were especially 

 plentiful in the hybrid already indicated as possessing a great 

 number of tubules (fig. 4). 



The germ-cells in many of the tubules were in process of degen- 

 eration. In some cases only a peripheral row of spermatogonia 

 and Sertoli cells remained but more commonly the cells progressed 

 to the spermatocyte type and then halted at the point of synapsis. 

 So common was this, indeed, that the characteristic appearance 

 of the tubules was that of a mass of cells in the contraction phase 

 of the primary spermatocytes (fig. 9). The deeply staining chro- 

 matin strands became massed at one side of the nucleus, commonly 

 lying in more or less of a crescent along the inner surface of the 

 nuclear membrane. Frequently such nuclei had a vacuolar, 

 abnormal appearance as if on the point of dissolution. Less 

 often the nuclei of the spermatocytes had a clear watery looking 

 center with the chromatin spread around the periphery. Not a 

 few syncytial masses existed containing numerous degenerating 

 nuclei, among which there were often evidences of fusion or of 

 direct division. 



As to why so many of the cells should be unable to progress 

 beyond the beginning of the synaptic phase I can offer no further 

 suggestion than that made in connection with a similar study^ 



* Guyer, M. F.: Spermatogenesis of normal and of hybrid pigeons. Disser- 

 tation, University of Chicago, 1900. Later published as Bui. 22, University of 

 Cincinnati, 1903. In case this pa{)er is inaccessible to any investigator, the author 

 will gladly supply copies as long as his stock of reprints lasts. 



