397 



regions outside of the sex-glauds. There are greater fluctuations in 

 these numbers than in those relating to the sex- cells of the sex-gland. 

 One of the most interesting and important phases of this work, 

 was the study of a couple of double embryos, one of Chrysemys mar- 

 ginata, Figs. 3 and 4, and the other of Chelydra serpentina. Fig. 5. 

 In the latter, it was impossible to count the sex-cells, but many could 



Fig. 3. 



Fig. 5. 



I 



Fig. 4. 



Fig. 3. A surface view of embryos 8 and 9 of Chrysemys marginata. 

 Fig. 4. Embryos 8 and 9 as seen in transverse section. 

 Fig. 5. Tlie double embryo of Chelydra serpentina. 



be positively identified. The very interesting fact was noted, that 

 they occurred in normal positions opposite the caudal portion of each 

 embryo. 



The double blastoderm of Chrysemys (embryos 8 and 9) was much 

 more thoroughly studied. Unfortunately, in the process of staining, 

 another slide was scraped over a portion of the sections in this series. 

 This necessitates the giving of the actual count and an estimate of 

 the complete number. This estimate is based upon the average number 



