68 PROCEEDINGS OF THE AMERICAN ACADEMY. 



(Figure I). It was captured in a house in Boston, where it had been 

 seen with a white and a black-white mouse. Unfortunately it died before 

 any young could be obtained from it. Its skin was soft, and it was sim- 

 ilar in every way to those figured by Gaskoin, save that the ears had a 

 few hairs on their distal portion, and there were a number of whiskers. 



During the course of the writer's experiments, a certain normally 

 haired female gave birth to a litter of young, and these, after acquiring 

 their first coat of hair, became sick and perished one by one, till finally 

 a single individual of the litter remained. This mouse, while still very 

 young, lost all its hair, except for a small amount on the ears, nose, feet, 

 and tail. It soon began to develop the transverse corrugations and the 

 lateral fold of skin, and would doubtless have become a " rhinoceros 

 mouse," had its career not been cut short at this interesting stage. It 

 is clear that this condition is a pathological one, and there are iiuiications 

 that it is heritable, but exact tests of this have as yet proved impossible. 



III. (-AKE AND Management. 



A few words respecting the care and management of mice may not 

 be without value to those who contemplate experimenting with these 

 animals. Tame white mice and rats seem to have little desire to escape 

 from their boxes, and hence cause little trouble. But wild individuals 

 are very timid and at the first alarm are apt to rush wildly for the near- 

 est opening, and escape. For this reason, it was found that a double 

 compartment cage, with separate doors for each compartment, was the 

 best. A small opening at the far end of the partition between the com- 

 partments allows the inmates to gain the shelter of the opposite cham- 

 ber while one side of the cage is being examined or cleaned. As the 

 results of experiments with various sorts of cages, Professors Mark and 

 Castle designed one which has been used in the work at the Harvard 

 Zoological Laboratory for the past two years with great satisfaction. As 

 the basis for the cage (Figure 2), a wooden tray is used, of the standard 

 size employed throughout the Museum of Comparative Zoology, viz., 27 i 

 inches long, 18 inches wide, and 3.V inches high, outside measurements, 

 made from half-inch stock. At the back of this tray, three upright posts 

 13 inches high are erected, one at either end and a third at the middle. 

 Cross pieces connect the tops of these posts, and two slanting side pieces 

 run from the tops of the end posts to the front of the tray. The sides 

 as well as a central partition are of wire netting, and the two doors, 

 hinged to the top, are wooden frames covered on the inner side with 

 netting. Racks were constructed, designed to hold ten or twenty of these 



