56 Journal of the Mitchell Society [September 



ground so closely that it is difficult to find, especially after the place 

 has become dry. 



In the beginning it Avas deemed best to allow the eggs to incubate 

 under normal conditions. A plan of marking the nests with stakes 

 was adopted. Soon it was found that these nests and many others 

 were opened by some animal, or animals, and the contents of the 

 eggs consumed. Nests were frequently found where the empty shells 

 had been replaced and covered over with loose dirt and sticks. Be- 

 cause of this, the plan of marking the nests was abandoned and all 

 the eggs were brought into the laboratory for artificial incubation. 



In the chick the eggs are so produced that they mature at con- 

 secutive intervals of time, approximately from twenty-four to forty- 

 eight hours apart, and are laid individually from day to day over a 

 considerable period. An examination of the ovary of the chick shows 

 a graded series of the eggs from the smallest ovarian egg up through 

 sizes to those with fully developed yolks just ready to be shed from 

 the ovary. In Chelydra serpentina this is not the case. Here, where 

 a large number of eggs are to be fertilized and laid a brief period 

 of time, are found two types of eggs: the small ovarian egg and 

 the mature egg which is ready to receive the white. The mature 

 eggs of C. serpentina are evidently developed simultaneously from the 

 ovarian egg in the season. In Chrijsemys cinerea, however, a much 

 greater period of time is required to build up the mature egg, pos- 

 sibly four years, since, according to size, the eggs usually occur in 

 four groups. The largest group is composed of eggs the yolks of 

 which are nearly as large as those in fully developed eggs. The sec- 

 ond group contains eggs about half as large as the first and the other 

 groups of eggs decrease in size correspondingly. Agassiz noted this 

 fact in C. picta and he assumed that it takes four years for the egg to 

 reach the stage where it is ready to receive the white. He stated also 

 that the number of eggs of a given size must represent the number 

 of eggs in a clutch laid by the species. This latter statement seemed 

 a valid assumption but present evidence from Chrysemys cinerea 

 shows it to be doubtful. Although specimens were dissected which 

 contained but one egg of a given size, many had groups of two or 

 three eggs. Since never fewer than four eggs were found in the 

 nest or the oviduct of the turtles examined, it would appear that the 

 small eggs may mature rapidly. 



