Foetal Membranes of the American Beaver (Oastor cauadensis). 197 



für, which is soft and silky to the touch, and of a clear brown, 

 with a slightly reddish tinge. In these skins the coarse tiaifs are 

 nndeveloped." 



My first beaver was taken on April 21st } from a trap which 

 had been set three days previously in the Murray river near a 

 beaver-burrow in the river-bank, no beaver-lodge occurring at that 

 spot. The beaver was a rather large pregnant female showing four 

 prominent pectoral teats, one pre-axillary and one post-axillary pair. 

 The presence of four pectoral mammae, a constant character of 

 the beaver, is mentioned by Audubon and Bachmann (1846) and 

 by Lewis Morgan (1868). The same character is met with in 

 the Canada Porcupine (Erethizon dorsatum) and in the Ceylon 

 Loris (Loris gracilis); in the latter all four mammae are post- 

 axillary. In each case the tetramerous arrangement has most cer- 

 tainly been acquired independently. a fact which adds considerably 

 to its interest. It is also a fact that the number of teats in these 

 forms bears no relation to the number of young. The Ceylon Loris 

 produces one young at a birth; the Canada Porcupine brings forth 

 1—2 young. The young of the beaver are stated to vary in number 

 from 2 to 5; but according to Moegan, an Ojibwa trapper named 

 William Bass, who was „extremely well versed in the habits of 

 the beaver" had „found 8 young beavers in a foetal State in one 

 female, and 8 young beavers born alive in a Single lodge. He had 

 also found six young ones a number of times, and all the numbers 

 below this down to a Single young beaver." Samuel Heaene (1795; 

 quoted by Morgan) who had exceptional opportunities for Observation, 

 having seen hundreds of them killed by the Indians in all stages 

 of gestation, „never could discover more than six young in one 

 female, and that only in two instances; for the usual number is 

 from two to five". 



The measurements of the beaver as she lay dead upon the ice 

 were as follows: — Total length 41 % inches, length of tail mea- 

 sured from the cloacal orifice 14% inches, length of scaly portion 

 of tail lO 1 /« inches. As mentioned above, there were four foetus 

 in the right Uterus only; the left uterus was empty and contracted 

 to a uniform diameter; but tlie left ovary presented the same 

 macroscopic appearance, dotted with small clear circular patches, 

 as tlie right ovary. 



The large uterine swellings or utricles, containing the foetus. 

 were separated by narrow constricted intervals (mter-utricnlar seg- 



