394 THE ZOOLOGIST. 



1st. The average number of young Adders at a birth. 



Various authorities give different figures : thus Dr. Stradling 

 puts the litter at from 15 to 40, M. C. Cooke at 10 to 20. My 

 own experience leads me to doubt very seriously whether Adders 

 ever have forty young at once. I have dissected now a consider- 

 able number of full-grown female Adders in young (three this 

 week), one of which I will now describe in detail. 



Dissection of Gravid Female. — On Monday, July 23rd, I dis- 

 sected a large gravid female Adder for the purpose of counting 

 the number of young that had developed. A mesial incision was 

 made from the position of the ovaries to the cloaca, and the skin 

 turned outwards. Both oviducts were full of eggs. The upper 

 and lower ends of the oviducts were tied with string, and the 

 other organs gently separated. Both oviducts were then lifted 

 out of the body cavity. The dissection showed the blood supply 

 very beautifully, and the young were evidently only a day or two 

 from birth. I took a photo of the full oviducts, as one cannot 

 often get an Adder at this stage. The right oviduct contained 

 seven and the left six eggs. (An egg often contains two embryos.) 

 The specimen was such a perfect one that I thought I would pre- 

 serve it in toto to harden, so as to observe later the precise 

 position of the embryo in the egg. This being so, I could not 

 be quite certain as to their number, but I think it is 19 or 20. 

 The average of this series of dissections works out at thirteen 

 embryos to each female Adder. (The eggs often contain more 

 than one embryo ; in this latter case there were thirteen eggs 

 containing the eighteen embryos.) Possibly a larger series of 

 dissections might give slightly different results, but I do not 

 think the difference is likely to be great. To be on the safe side 

 (as far as the question of capacity is concerned), let us consider 

 the average to be fifteen, 



2nd. The anatomical fitness of the gullet for their reception. 



This is soon disposed of, as the Adder's gullet is, of course, 

 adapted to its food. There is no difficulty whatever for a Mouse, 

 a young Water Vole, or a Blindworm to pass into the gullet, and 

 it is quite easy to press them out again if they are contained 

 therein. (A short time ago I killed an Adder which appeared 



