Early Development of Desmogiiathus Fusca. 535 



were made so far as possible upon living specimens ; this was possible 

 in earlier stages, but more difficult in later development. The obser- 

 vations on the living eggs were confirmed and supplemented by a 

 study of corresponding stages of preserved material with serial sec- 

 tions through selected embryos. 



Great difficulty was experienced in the removal of the egg mem- 

 branes and if these were left on, the surfaces were injured by 

 osmosis in the alcohols. If eggs are fixed in formalin this may 

 be avoided. Although the membranes are rather difficult to remove 

 with instruments they may be easily dissolved by a weak solution of 

 potassium hypochlorite. Eggs which have been preserved in formalin 

 do not cut very well in paraffin, although they cut easily in collodion 

 and quite well in collodion and paraffin combined. Formalin pre- 

 served eggs are good for external study, the natural colors and mark- 

 ings are so well retained, but they are soft and have to be handled 

 with great care after the membranes have been removed. Perenyi's 

 mixture as a fixing agent, in certain respects was very useful. The 

 form was well preserved and the eggs so hard that they could be 

 handled without danger of injury, but they were not so good for 

 sections. The killing mixture which gave the most satisfactory 

 results for sections in paraffin was Gilson's fluid, as the yolk re- 

 mained soft after treatment with this reagent. 



Practically nothing is known about the mating of Desmognathus 

 fusca. The eggs obtained in central and southern ISTew York were 

 found from the last of June to the middle or last of July. The only 

 case in which the female was found laying was early morning shortly 

 after daylight, this same female when taken to the laboratory soon 

 deposited two other eggs. Judging from the stage of development of a 

 number of egg masses it seems probable that quite a number are laid 

 at night. One bunch of eggs found late in the afternoon was un- 

 segmented. 



The eggs are about fifteen or twenty in number, usually grouped 

 together in a single package under logs or stones in moist, or rather 

 wet locations with the body of the female arched about them in the 

 form of a semi-circle. The presence of the female seems to furnish 

 sufficient moisture rather than anything else, for when she is 



