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R. R. HUMPHREY. 



the growth and divisions of its spermatocytes, the slender caudal 

 appendage is naturally in obvious contrast as to size (Fig. 4). 

 In the fall, after extrusion of the spermatozoa, the testis proper is 

 greatly reduced in diameter; the appendage, meanwhile, has 

 become considerably enlarged. During the winter, as a result, 

 the testis appears of more nearly uniform diameter throughout, 

 as in Fig. I, with little or no indication of the caudal reduction so 

 striking in the preceding summer. Nevertheless, in the spring 

 the appendage once more makes its appearance. 





FIG. 8. Caudal third of the testis of Plethodon gliilinostts in late June. Semi- 

 diagrammatic. The reduction in size of the lobules of the caudal appendage is 

 strikingly shown; but little debris from degenerating cells now remains. Though 

 the body of the testis at this season contains transforming spermatids, the lobules 

 of the appendage show only occasional germ cells other than their apical spcrma- 

 togonia. T.s., transforming spermatids; l.c.d., longitudinal collecting duct, 

 central in position, surrounded by connective tissue; p. s., primary spermatogonium 

 (residual spermatogonium) of lobule apex; d., nuclear debris from recently de- 

 generating germ cells; i.e., interstitial cells; sp., group of spermatids; 5., a primary 

 spermatocyte. 



Examined in sections, the appendage of a male killed in early 

 June is found to be traversed by the central collecting duct of the 



