THE MULTIPLE TESTIS OF URODELES. 



49 



The structure of the urodele testis has been described at length 

 in a previous communication and need be only briefly reviewed at 

 this time. The elongated testis is suspended from the dorsal ab- 

 dominal wall by a mesorchium in which run the blood vessels and 

 efferent ductules. The latter, varying from few to several in num- 

 ber, lead from the longitudinal collecting duct of the testis to the 

 ductus deferens (Wolffian duct). The longitudinal collecting duct 

 may be superficial in position, or as in many urodeles, more cen- 

 trally located. The structural units of the testis, the lobules, 1 

 empty into the longitudinal collecting duct either directly, by 

 means of very short ducts, or more indirectly, by way of longer, 

 much-branched tributary ducts. 



FIG. i. Longitudinal section of the extreme anterior end (primary germ- 

 cell cord) of a Desmognathits testis. The longitudinal collecting duct is 

 shown, bordered by primary spermatogonia. The caudal germ-cell cord 

 remaining after the complete degeneration of the lobules is essentially the 

 same structure, as is also the slender cord intervening between successive 

 lobes. The primary spermatogonia, in these latter structures, are properly 

 termed " residual " spermatogonia. 



A study of the lobule itself shows it to be a structure made up 

 of reproductive cells all in approximately the same stage of de- 

 velopment. Figure 2 shows the lobules as hollow cyst-like cham- 

 bers lined by spermatogonia. All the cells in a lobule undergo 

 their developmental transformations synchronously, mature as 

 spermatozoa and leave the lobule. There remain behind only the 

 Sertoli cells which soon degenerate and disappear and the re- 

 sidual spermatogonia. The latter are germ cells located only in 

 the apex of the lobule, where it joins the collecting duct system. 



i The term lobule, introduced by Kingsbury ('02), is used here in preference 

 to the terms "cyst," "capsule," "tubule," etc., employed by various inves- 

 tigators. 



