A MODIFICATION OF THE URODELE TESTIS. 



147 



testis in Ambystoma, or the bluntly-rounded termination of the 

 organ in other L rodele males lacking an appendage. 



To understand the origin and significance of the appendage it 

 i- necessary to note its seasonal changes, both in gross appearamv 

 and in histological detail. These will be first outlined as they 

 occur in Plethodon glntinosus, a species in which the appendage 

 ib prat tically a constant feature in the adult mak-. It is ni"-t 

 <.ii-pirii<>n- in animals killed from May to July. Siii'-e the body 

 <>1" MM testis i- tlit--ii approaching its maximum dianu-u-r. dm- to 



I 34567 



I i' ~. A scries of diagrams to illustrate v.u: rma >f th- 



common:- ,-d in L'rodeles. The cephalic end of the t -:pperm. 



IK. i. 1 I. cylindrical type of testis. tapering anteriorly, bluntly 



roun : ly. Found in the I'lethodons, Eur: < >inophilu<; during 



winter in.. ii 1 . in some males of these species, in surnn 



.ition of the lestis of Fig. i resulting iroin i-arlier emptying of 



the t.ui'lal lobules. The anterior lobules still contain sperm. it"/- a, A : tis of 

 -.intered during the fall or early winter months in the 1M. tli'-loii-; 

 oth. md is reduced to the type of Fig. i by the final emptying ot the 



lobuli 



:i of the testis of Fig. i resulting fpni . ,u pm.-nt 



of the germ i.-iU in ca;:dal lobules. Seen as a rule in spring months or in young 

 male- m \\li : proportion of the lobules produi 



.th a caudal reduction ("caudal append. i ulting from 



s in the caudal lobules of the organ. Found commonly in 



Pletlioiii": :mg the summer months; less common in l-'.urycea and 



ho dun chifrius. 



Fn.. ;. ! ih a constriction resulting from localized germ-cell degenera- 



tion. 1 -'..1111.1 on] :lly, sometimes as an apparent preliminary condition 



to that illustrated in Fig. 4. 



1 i.. . " Multiple testis" of Desmognathus resulting from delayed regeneration 



xual cycle. Spermatozoa for the following cycle are 

 alw.r in lobules ahead of those maturing germ cells in the current so:; 



FlG. .. 1 ."/i i/us in summer. In this the caudal ap- 



pendage. though structurally similar to that of Plethodon glntinosus (Fig. 4) is 



by the greater length and reduced diameter of the organ 

 ; whole. 



