204 MICHIGAN ACADEMY OF SCIENCE. 



10. Rather quiet in daytime; more active at night. 



11. The animal ordinarily defends itself by striking with its fore feet; it bites 

 only when grasped. 



12. Its actions are very different in an unfamiliar locality. 



13. Does not fully appreciate height,2 — a trait connected with its aquatic habits. 



Legends for Figures. 



Fig, 1. Showing position of teeth when at rest. 

 Fig. 2. Showing method cf sharpening the lower incisors. 

 Fig. 3. Showing method of sharpening the upper incisors. 

 Fig. 4. Appearance of incisor teeth when captured. 



Fig. 5. Showing the V-shaped wearing of the lower incisors and the corre- 

 sponding notch in the upper incisors. 



2 No experiments were made to determine what the muskrat's actions would be when placed at a 

 greater height above the floor. The difficulty with attempting to make such experiments is that the 

 animal would have to be placed under conditions strange to him, and fear— if that be the proper 

 word for the uneasiness that many animals exhibit at such times — then predominates, and makes 

 results uncertain. The muskrat was familiar with his cage, and when the door was left open with- 

 out calling him to take food, there was no danger of his falling out if he chanced to come to the door 

 of his own accord. He apparently, at such times, appreciated the distance to the floor and the 

 danger of a fall. But owing to his habits in his natural aquatic environments, this appreciation was 

 not Ingrained, as it. is in a squinel for mstance, and when his attention was concentrated on getting 

 the food which he expected, it failed himj 



