f028 FRESH- WATER BIOLOGY 



graphic, and Blanding's turtles, and above all, the terrestrial and 

 perfectly-armored box turtle, are the gentlest of creatures which no 

 amount of provocation will induce to bite. Although the correla- 

 tion between armature and disposition is very striking there may 

 be no causal relation between the two. The character of the food 

 may be the cause of the disposition. 



Batrachians 



The batrachians, as a group, are aquatic to a much greater 

 degree than the mammals or reptiles. In North America they are 

 summer and especially spring members of the aquatic fauna. 

 Some of them, with all their ancestry, have been strictly aquatic. 

 They are autochthons, products of evolution in fresh water. Such 

 aquatic forms have gills and a tail throughout life. The Siren and 

 the mud puppy, of deadly repute, belong to this group and so does 

 the bhnd salamander of Texas. Whereas in the reptiles and the 

 mammals gradations from pure terrestrials to less or more aquatics 

 have been noted, in the batrachians one finds gradations from the 

 purely aquatic to the more or less terrestrial, and none have reached 

 the possibihty of Hving in deserts in dry places. So many of the 

 batrachians lay their eggs in water that those that do not are 

 accounted remarkable. In a small pond near Indiana University, 

 which has been examined at ail seasons of the year, it has been 

 found that a salamander, Amblysioma jefersonianum, begins to lay 

 as soon as the ice disappears after December. Sometimes this 

 happens early in January or it may not until March. After the 

 spawning of jeffersonianum comes that of AmUystoma punctatum. 

 Both deposit their eggs in jellylike clumps. Hyla pickeringii and 

 .4 cm gryllus spawn in the same pond between early March and late 

 May. During late spring and early summer the newt, Diemictylus 

 viridescens, spawns here. Very frequently this pond dries up in 

 summer, and then there is an opportunity to see how any of the 

 aquatic batrachians may become terrestrial. Late in summer Am- 

 blysioma opacum spawns in this pond. Usually the pond is dry at 

 the time, whereupon the salamander lays its eggs under leaves or 

 under a board, coiling itself about the eggs. The hatching of such 



