THE MULTIPLE TESTIS OF URODELES. 63 



result in the formation of shorter lobes and permit the establish- 

 ment of a greater number before a cephalic running out of the first 

 lobe occurred. It seems probable that the presence of several 

 lobes is of itself a factor in reducing wave rate. When a large 

 number of lobes is present, each lobe is shorter, as a rule, than 

 those of males with a smaller number. This acts, of course, in a 

 full-grown animal, to keep the total functioning volume of the 

 testis a constant as new lobes are added. 



In the preceding consideration of the effect of wave rate it has 

 been assumed that the time elapsing before lobule regeneration 

 occurs has not been affected. This, however, is probably subject 

 to the influence of metabolic conditions in the same way as is wave 

 rate. We may safely assume, I believe, that lobule regeneration 

 could be somewhat hastened by very favorable conditions or de- 

 layed by unfavorable ones. The effect in the first case would be 

 to reduce the length of the interval between lobes, and therefore 

 permit the establishment of a greater number; the effect in the 

 second case would be of the opposite nature. 



Favorable metabolic conditions, therefore, would tend to in- 

 crease the wave rate and through it the size of the lobes, reducing 

 at the same time their possible number ; the same conditions, how- 

 ever, would probably cause earlier regeneration, shorten the inter- 

 val between lobes, and tend thus to permit a greater number. Un- 

 favorable conditions, by slowing the wave rate, shorten the lobes 

 and thus increase the number possible; the same conditions, 

 though, would tend to delay lobule regeneration and the formation 

 of new lobes, increase the interval between lobes, and reduce the 

 number. The net change, so far as the functional volume of the 

 testis is concerned, is small; and excessive increase or reduction of 

 the total output of reproductive cells will not occur, in a fully 

 developed male, except under very unusual conditions. 



The writer, therefore, though agreeing that bodily vigor may 

 influence lobe number, insists that it does so only by affecting the 

 length of the primary germ-cell cord, modifying the rate of the 

 spermatogenetic wave, or changing the time necessary for lobule 

 regeneration. In other words, given a spermatogenetic pattern 

 such that multiple testes are possible, the modification of this pat- 

 tern, by whatever influences it may be brought about, inevitably 



