Vol. XXVIII, pp. 61-68 March 12, 1915 



PROCEEDINGS 



OF TH?: 



BIOLOGICAL SOCIETY OF WASHINGTON 



THE VARIATIONS OF A BROOD OF WATERSNAKES. 



BY E. R. DUNN. 



On June 22, 1914, 1 caught a female Natrix sipedon, in James 

 River near Midway Mills, Nelson County, Virginia, about 40 

 miles below Lynchburg. The river all along here is swift and 

 shallow. There are many low islands covered with heavy grass, 

 where the snakes hide. The most common fish is the spotted 

 catfish, Ictalurus punctatus, which has been introduced from the 

 West, and these form the chief food of the snakes. 



I kept the female in company with several others of her own 

 species. She showed a larger appetite than any of the others, 

 eating toads, frogs, tadpoles, and small fish, whenever any were 

 offered to her. She shed her skin on July 10, and again on 

 August 19. The other females with which she was confined 

 gave birth to young as follows : two on August 19, and one on 

 each of these dates, August 21, 24, 26, and September 3. This 

 particular specimen, however, did not give birth till October 12. 



I observed the birth of most of her brood. The mother 

 crawled around the cage with her tail raised and every now and 

 then she expelled from one to three eggs. The covering of these 

 was transparent and the young could plainly be seen. They lay 

 still for a few moments, then struggled to break the sac and 

 thrust out the head. After accomplishing this, they lay quiet 

 another minute, thrusting out the tongue, and then crawled off, 

 at once becoming very lively. As soon as they dried off, they 

 began to shed the skin. I could observe no egg-tooth in these 

 young snakes. 



Originally there were 37 live young, two nearly developed 

 embryos, and one which did not succeed in bursting the egg 

 sac, and so died. Seven, however, were eaten by a large bull- 



8— Proc. Biol. Soc. Wash., Vol. XXVIII, 1915. (61) 



