234 B. F. KINGSBURY AND PAULINE E. HIRSH 



of the year, mature or maturing spermatozoa fill the lobules at the 

 cephalic end while primary spermatogonia occupy the caudal 

 filament of the gland, successive stages occupying in orderly 

 sequence the intervening groups of lobules. Compare Kingsburj^ 

 ('()2), text figure A. 



In Desmognathus, in the spring and in some cases in early 

 summer, the transition from spermatogonia to mature spermato- 

 cytes I, as shown in longitudinal section of the organ, is gradual, 

 but as the season advances a 'boundary plane' between those 

 destined to furnish spermatozoa that season and those that will 

 hold over becomes more and more evident. The 'spermatoge- 

 netic wave' has stopped short at a particular point; the progressive 

 changes of spermatogenesis continue in one portion and lag or 

 are lacking in the other portion; and it is in those lobules just 

 behind (caudad of) this boundary that the degenerations are 

 constantly found. 



How striking this boundary between the two regions becomes 

 may be seen by comparing figures 1, 2, 6 and 3 which reproduce 

 longitudinal sections of the testis- of Desmognathus from the 

 months of May, June, August and September respectively, the 

 transverse lines drawn upon the photograph indicating the plane 

 of boundary which in figure 1 is not yet established as such. 

 Figures 4, 7, and 5 give enlarged views of the region of the bound- 

 ary and in them the cysts and lobules filled with degenerating 

 cells are seen. Figure 7 is from a section neighboring that shown 

 in figure 4 which is an enlargement from figure 2, while figure 5 is 

 an enlargement from the section of figure 3. As is well recognized 

 in urodele spermatogenesis, the cells contained in and composing 

 a cyst are in the same or closely contiguous stages of develop- 

 ment, and while in some instances, cells occur singly or a few 

 together, in the great majority of cases, the contents of the entire 

 cyst or even lobule are undergoing degeneration together. In the 

 degenerating cysts and lobules however it is the germ cells and 

 not the follicle cells forming the cyst wall that degenerate, the 

 nuclei of the latter being apparently normal and distinguishable 

 amid the degenerating spermatogonia as Hermann pointed out 

 and figured. Figures 8 and 9 show degenerating lobules while 



