LIFE HISTORY OF DESMOGNATHUS FUSCA. 307 



masts, are also prominent features of the skin during the entire 

 larval life. They remain in practically the same condition except 

 that as the skin becomes thicker and more compact, the accessory 

 cells of the neuromasts become more numerous and more closely 

 crowded together. Organs of this type are said to be associated 

 with aquatic life and to be adapted to the reception of pressure 

 stimuli. In view of this, it is interesting to note that the neuro- 

 masts are probably connected with the ready response of the 

 larva both to a slight increase in the depth of the water above it, 

 and to mechanical pressure applied to opposite sides of the body. 



METAMORPHOSIS. 



Metamorphosis occurs, as above stated, in late spring. The 

 earliest date at which I have collected larvae showing signs of 

 the approaching change is May n, the latest is June 17. There 

 is strong evidence, however, in the histological conditions and 

 body proportions of the small adults of from 33 mm. to 35 mm. 

 in length which I have collected early in June, that they have 

 only recently undergone metamorphosis, and adult specimens 

 of similar size and proportions may be collected in early fall 

 also (Table II. and Graphs III. and IV.). It thus seems probable 

 that the period of metamorphosis may begin as early as May 

 and may extend well into the summer, a range of time comparable 

 to that known to exist for both the egg-laying and the hatching 

 periods. 



Larvae which are undergoing metamorphosis are usually not 

 found in the water but among the dead leaves and loose debris 

 along the edge, often headed away from the water as if they were 

 in the act of crawling out of it. 



The noticeable changes in external appearance which take 

 place during the process are the following: 



1. The body proportions change, the head becoming relatively 

 shorter and its posterior region narrower and the tail longer. 



2. The median fin fold characteristic of the aquatic larval 

 period undergoes atrophy, the cross section of the tail thus 

 acquiring a more rounded contour. 



3. The gill bushes gradually diminish in length, each filament 

 becoming blunt at its extremity instead of slender and pointed, 



