278 Susanna Phelps Gage 



red stage the metapore is larger and by the end of terrestrial 

 life the condition is practically the same as in the adult. 



The pia and arachnoid are more clearly defined in the red 

 stages than in others, as owing to the more rapid growth of 

 the skull, the brain does not fill the cavity, and appears hung 

 in sheets of pia and supported by a spongework of arachnoid. 



In early stages the dura has only a few pigment cells where 

 it is in contact with the epidermis on the dorsal side, these in- 

 crease gradually ventrad but even in the large red forms where 

 the pigment is scattered throughout the dura, it is small in 

 amount and of a brown color. The great increase of pigment 

 in the dura seems to be associated with large size in the adult, 

 and in one very marked case, with a shrunken condition of the 

 brain. 



The endolymphatic sacs in the larval forms are small, in 

 the red forms the relations of the parts are clearer than in the 

 adult (Fig. 8) because the sacs apparently are not so convo- 

 luted. 



Between the brains of the adult male and female there ap- 

 pears to be no difference other than occurs between individuals 

 of the same sex. 



SUMMARY. 



From the above detailed description it is seen that the brain 

 of Dierayctylus resembles, in its embryonic, young larval and 

 adult stages, the brain in corresponding stages of other Uro- 

 deles ; and that there are no marked changes in the mor- 

 phology of the brain corresponding to the crises of develop- 

 ment and change in structure and function of the animal. 

 After the earliest stages of larval life, the parts of the brain 

 develop gradually, one after the other acquiring its mature 

 form, at periods which have no exact relation to those crises. 

 There is, however, a marked general growth at about the time 

 of final transformation so that the brain much more nearly fills 

 the skull than in the late red forms. 



The grosser morphological plan was laid out before hatch- 

 ing, the details are added by gradual growth. It is possible 

 that in the finer structure of nerve cells, in the path of nerve 



