2 Primitive Streak and Notochordal Canal in Chelonia. 



to dry. Indeed, in one instance the female— Chelopus insculptus- 

 was found in the act of laying, and the eggs were taken from thi 

 uncovered nest. The nest was of the same form as that describee 

 by Professor Agassiz ('57, p. 500) for Chelydra serpentina. Thi 

 perpendicular excavation was about five inches deep. From th( 

 bottom of this excavation a chamber extended horizontally fo 

 some three or four inches. The female stood over the externa 

 opening in such a manner that the axis of her body was parallel t( 

 and directly above the horizontal chamber. The blind end of th( 

 horizontal chamber pointed anteriad in relation to the axis of he 

 body. During each act of deposition she pressed the cloacal enc 

 of the body as far as possible into the perpendicular hole and le 

 the egg fall to the bottom. Then she extended one hind foot intc 

 the hole and pushed the egg anteriad into the horizontal chamber 

 What seemed remarkable to me was the fact that she used the lef 

 foot to arrange one egg, then the right foot for the next, and so 01 

 alternately for the eight eggs she had to deposit. Did a depositiot 

 of the egg from the right or left oviduct induce this alternation o 

 foot movement? Do the eggs come alternately from the righ 

 and the left oviduct t 



An effort was made to obtain eggs from females kept in con^ 

 finement ; but, although males and females were kept in a pen ou' 

 of doors with sufficient food, — earthworms, — and with water foi 

 swimming, no eggs were laid by the end of June. The females 

 were then chloroformed, and unfertilized eggs were found stil 

 retained in the oviducts. 



Since all attempts to gain fertilized eggs from captive turtles 

 failed, all the embryos described in this paper were taken frore 

 eggs laid by free turtles. Upon removal from the nest, the eggs 

 were packed in m&ist sand and thus transported to the laboratory 

 As soon as possible after arrival in Cambridge the embryos were 

 removed from the eggs, not longer than two or three hours aftei 

 their first discovery. 



During the early stages, as Mitsukuri ('93, p. 230) has already 

 said, the embryo is not yet attached to the shell ; therefore, if pre 

 caution against desiccation is taken, the eggs may be transported 

 with perfect safety to the embryos. 



In order to remove the embryo, the egg shell was broken anc 

 a portion carefully torn away by means of forceps. When a suffi- 

 ciently large opening had been made, the whole contents were 



