LIFE HISTORY OF DESMOGNATHUS FUSCA. 323 



portions from those at metamorphosis to those of the final adult 

 life, a change which involves a relatively more rapid growth of 

 the caudal than of the other regions, also takes place more rapidly 

 during the first two years (cf . Table II., Graphs III. and I V.) . All 

 of the adults, however, show a slight range of variation in the 

 proportions of length of body regions which is in general corre- 

 lated with the size of the specimens, as if the caudal region 

 continued always to grow slightly more rapidly than the rest of 

 the body. Here, however, the actual facts are sometimes 

 masked by the frequency of regeneration of the tail, since a 

 large percentage of adults show the tail to be in some stage of 

 regeneration. I have seen no evidence that this loss of tail is 

 due to self-mutilation as in the case of Plethodon, although the 

 natural supposition would be that such is the case. Such 

 regenerating specimens have, when detected, been excluded 

 from my statistics, but when the process of tail regeneration is 

 nearly complete, it is not always possible to decide whether the 

 specimen presents a case of regeneration or one at the lower limit 

 of normal variation. The question of the time of sexual maturity 

 may also throw some light on the duration of the period of the 

 more rapid growth of adults. At the time of metamorphosis the 

 two sexes may be distinguished by the histological condition of 

 the germ cells, some of the ova having already entered upon the 

 growth period. Small adults, up to the 43 mm. stage, i. e., 

 presumably of a year's growth as adults, give no indication of 

 sexual maturity. I have had too little opportunity to examine 

 in this particular, specimens of the next larger size, presumably 

 of two years' growth, to be able to state definitely that they may 

 not be sexually mature at this time, but the few that I have 

 examined were not so. On the other hand, specimens of 68 mm. 

 and over of both sexes are sexually mature, apparently after 

 three years of adult life. In the mating season the lips of the 

 cloaca are often somewhat everted, and the two sexes may be 

 distinguished by the fact that the female cloacal lips display 

 numerous folds which converge anteriorly, with an anteriorly 

 projecting papilla in the mid-line at the posterior angle of the 

 two lips. In the end of this papilla, which lies within the cloacal 

 cavity, is the orifice of the spermatheca. The lips of the male 

 cloaca are thickly covered with villi-like processes. 



