1933] Phases in the Development of Chrysemys Cinerea 61 



blastopore stage and remained in that stage. Evidently some condi- 

 tion arrests the development of most of the eggs about the time the 

 blastopore is formed. Several attempts were made to determine the 

 factors which inhibited development. It was thought at first that 

 possibly the egg absorbed water from the soil, since soon after deposi- 

 tion the egg became turgid. To test this idea, uterine eggs were 

 weighed immediately upon their removal from the oviducts, then 

 placed under incubation conditions and weighed from time to time. 

 There was a slight decrease in weight indicating that water was not 

 absorbed from the outside during the development of the egg. Eggs 

 were also incubated under moist conditions without contact of soil 

 and were found to develop normally, indicating that soil has nothing 

 to do with the initiation of development. This left only the assump- 

 tion that either the gases of the air or those dissolved in water were 

 responsible for the renewal of embryological processes. Whole ovi- 

 ducts containing the eggs were removed, tied at each end and placed 

 under incubation conditions, but without results. The failure of these 

 eggs to develop, however, might reasonably be traced to the decay 

 of the tissue of the oviduct. Further experimentation will be carried 

 out along this line. It is quite possible that the physical change in 

 the shell from the hard, inflexible shell in the oviduct to the soft, 

 flexible shell in the nest permits a freer flow of gases. At any rate, 

 this renewal of development is co-incident with a change in the al- 

 bumen from a thick to a thin substance, with a corresponding in- 

 crease in pressure. 



While as a rule the eggs taken from the oviduct are in the blasto- 

 pore stage, some of them are found in the cleavage stages and others 

 in the earliest flexure stages. Embryo No. 38, fig. 33, was found 

 to be in this flexure condition. This was the second egg to enter 

 the oviduct and it was opened immediately upon its removal. This 

 embryo shows a greater development than those behind it in the 

 oviduct. 



Agassiz noted that a turtle might lay eggs that had been retained 

 for a considerable time. He found, however, that in most cases 

 such eggs developed into monstrosities. 



This is not necessarily true as is shown in the following experi- 

 ment. A turtle was caught, June 12, in the act of digging a nest. 

 She was placed in a tank of water, without sand, and kept until 

 July 10, when she was dissected. Of the seven eggs covered by shells, 



