1922] Phases in the Development of Chrysemys Cinerea 63 



placed in a box of sand, without any reference to their previous 

 position, and carried about one hundred miles to the laboratory, 

 where they were placed in a bucket of moist dirt which was cov- 

 ered with a bell jar. About the middle of September four little 

 terrapins of an undetermined species made their appearance. It is 

 surprising, when the careless handling of these eggs is considered, 

 that they hatched, for if such treatment had been given the eggs of 

 Chrysemys cinerea, the embryos would have died. This indicates a 

 fundamental difference in the egg structure of these two forms; the 

 blastodisc of this terrapin t^^, like that of the hen's eg^, did not 

 stick to the shell membrane but rotated as the egg was placed in 

 various positions. In the summer of 1919 the eggs of the painted 

 turtle were brought into the laboratory of the University of Wis- 

 consin and placed in buckets of dirt, covered with bell jars. From 

 such eggs embryos were secured. In these experiments newly laid 

 eggs (not over a few hours old) and uterine eggs were used. The 

 former were frequently collected before the the completion of the 

 packing of the hole of the nest but never before the laying was 

 finished. Uterine eggs were removed directly from the female. A 

 summary of the results of the incubation of the uterine and the laid 

 eggs for the first summer is here given : 



Total No. Total No. Total No. Per Cent 



Clutches Eggs Embryos Development 



Laid 6 32 11 34.4 



Uterine 19 135 99 73.3 



During the second and third summers practically none but uterine 

 eggs were used, but owing to the fact that many turtles were taken 

 before the copulating season began, the data on fertility would be 

 unreliable, and is therefore not included. 



Uterine eggs of other species have been examined by other stu- 

 dents, but no reports have been found which would indicate that 

 the incubation of uterine eggs had ever been attempted. The value 

 of such incubation will be pointed out later in the paper. 



Although it is necessary to kill the turtle to secure the uterine 

 eggs, this has its recompense, since from four to ten eggs are secured 

 from each turtle. These represent various stages of development 

 between early cleavage and the first flexure stages. Such a variety 

 of phases in a single individual does not seem to be available in 

 any other animal. If the turtle is taken early in the breeding sea- 



