CASTOROLOGIA. 



177 



sumes the form of regular scales closely resembling those of fishes. 

 It is not impossible that the tail may have the power of absorbing 

 water, like the skin of frogs, though it must be owned that the scaly 

 integument which invests that member has not much of the char- 

 acter which generally belongs to absorbing surfaces." 



Mr. Morgan's description, illustrated by the accompanying photo- 

 engraving (direct from nature), is very exact and the subject may be 

 concluded by the following extracts from his account : "In form, 

 structure, and uses, the tail is the most conspicuous organ of the 

 beaver. It is nearly flat, broad and straight, and covered with 

 horny scales of a lustrous black. These scales, which are such in 

 appearance only, cover every portion of the surface both above and 

 underneath. The tail is attached to a posterior projection of the 

 body extending some inches beyond the pelvis, and is furnished with 

 strong muscular attachments, by means of which its movements are 

 determined. Its principal uses are to elevate or depress the head 

 while swimming, to turn the body and vary its direction, and to as- 

 sist the animal in diving. It is also used to give a sign of alarm to 

 its mates. When alarmed in his pond, particularly at night, he im- 

 mediately dives, in doing which the posterior part of his body is 

 thrown out of water, and as he descends head foremost, the tail is 

 brought down upon the surface of the water with a heavy stroke, 

 and deep below it with a plunge. 



' ' I have heard it distinctly for half a mile, and think it can be 

 heard twice or three times that distance under favorable conditions. 



" It is capable of a diagonal movement from one side to the other, 

 and vice versa, and also of assuming a nearly vertical position. This 

 enables them to use it as a scull, which they do when entirely under 

 water, and swimming at the most rapid rate. It is most flexible at 

 the intersection of the tail proper with the posterior projection of the 

 body to which it is attached. The muscles for its down motion are 

 several times stronger than for either its upward or lateral move- 

 ments. He is able to turn his tail under him and sit upon it, or to use 

 it extended behind him as a prop while sitting upon his hind feet. 



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