B. F. Kingsbury 107 



multiplication, may furni&h the cells for a new formation of the lobule 

 in a succeeding season. McGregor, 99, was inclined to believe that the 

 cells which replenish the lobule came from the cells, forming the ducts 

 of the lobules. This seems hardly probable, since the collecting duct 

 and its branches appear to be developed from the mesonephros, Hoff- 

 mann, 86, and not from the germinal epithelium. I believe therefore 

 that residual spermatogonia occur in Amphiuma as they do in Desmog- 

 nathus, but were not recognized as such. In other salamanders, as 

 Spelei'pes, regeneration of the lobule begins before the spermatozoa leave 

 it. This does not seem to occur in Desmognathus, so that when the 

 lobule is regenerated, it is as a new formation. 



In Desmognathus, the spermatogenetic wave passes over the testis in 

 a forward direction, that is, from the caudal to the cephalic end. 

 There are encountered in an organ at the proper season of the year, 

 a succession of lobules containing ripe spermatozoa, maturing sperma- 

 tozoa, spermatids, speimatocytes, maturing and in division — second 

 growing spermatocytes (of the first order), secondary spermatogonia, 

 and finally primary spermatogonia in the more filiform cephalic end to 

 which the organ tapers. At the opposite end the organ also becomes 

 constricted, general!}'' more abruptly, where it passes into the mass of 

 interlobular connective tissue, which became more prominent when the 

 lobules shrank and disappeared. The testis accordingly has a rather 

 fusiform shape, tapering at both ends to a filament. The accompanying 

 diagram indicates the succession of regions in the testis of a specimen 



Fig. a. Diagram of a longisection of the testis of Desmognathus during July, to 

 show the succession of regions, a. primary spermatogonia ; 6. secondary spermato- 

 gonia; c. growing spermatocytes; d. zone containing dividing spermatocytes of the 

 tirst order and spermatocytes of the second order, resting and dividing; e. sperma- 

 tids; /. transforming spermatids and immature spermatozoa ; ^. ripe spermatozoa; 

 h. " degenerated" lobules. 



killed in July, as seen in longisection. The shape and size of the 

 organ, as is evident, is variable, depending on the time of year, being 

 larger in the summer than at other seasons, and of a correspondingly 

 different shape. Occasionally, and perhaps usually, it consists of two, 

 three or even four enlarged portions in which the spermatozoa are 



