ZOOLOGY AND BOTANY, MICllOSOOPY. ETC. Jl." 



the typical effects of extracts of the posterior lobe of Mammals, namely 



rise of blood-pressure, dilatation of the kidney, and increase of urine. 



Dancing- Mouse.* — R. M. Yerkes has studied the behaviour of this 

 domesticated animal, of unknown origin, which is characterised by its 

 inability to move far .in a straight line without whirling or* circling 

 about with extreme rapidity. The author can find no satisfactory 

 grounds for regarding the dancer as abnormal or pathological. It is a 

 peculiar variation which has been the subject of artificial selection. 

 Yerkes has experimented as regards hearing, vision, edncability, 

 duration of habits, and individual differences in behaviour. He found 

 no evidence of the transmission of an acquired habit of behaving 

 advantageously. 



Though able to squeak, and though capable of ear movements as of 

 listening, the dancing mouse is quite deaf, except, in some instances, 

 during the third week of life. Brightness-vision is fairly acute ; colour- 

 vision is poor — most of their apparent discrimination of colour is due to 

 differences in brightness ; form is not clearly perceived ; movement is 

 readily perceived. 



The mice learn to use a swinging door that has to be pushed on one 

 side and pulled on the other ; they are not helped by seeing other mice 

 do a thing, but are helped by being put through it themselves ; certain 

 acquired habits were remembered after 2-8 weeks of disuse ; if forgotten, 

 re-learning was easier. Initiative and plasticity do not decrease up to 

 an age of 18 months, the oldest studied. 



Yerkes' method consisted in a sort of " Lady or the Tiger " alterna- 

 tive presented to the unsuspecting mouse. He is invited to enter one 

 of two doors : one leads to an electric shock, the other to freedom and 

 food. The doors are marked by different signs — cards of different 

 shapes, markings, colour, brightness, odour, etc. — and these can be 

 readily alternated. The mouse tries at first the plan of returning to 

 the right or left door according as he has found that to be correct ; 

 when he finds that the correct portal is being alternated, he learns to 

 alternate in his choices ; when there is no regularity in the changes, the 

 mouse uses all its senses in determining which is the correct door to 

 enter, and learns finer and finer shades of discrimination. 



" Most Mammals which have been experimentally studied have 

 proved their eagerness and ability to learn the shortest, quickest, 

 and simplest route to food without the additional spur of punishment 

 for wandering. With the dancer it is different. It is coutent to be 

 moving — whether the movement carries it directly to the food-box is of 

 secondary importance. On its way to the food -box, no matter whether 

 the box be slightly or strikingly different from its companion box, the 

 dancer may go by way of the wrong box, may take a few turns, cut 

 some figure-eights, or even spin like a top for a few seconds almost 

 within vibrissa -reach of the food-box, and all this even though it be very 

 hungry." 



* The Dancing Mouse : a Study in Animal Behaviour. New York : The 

 Macmillan Co., 1907, xxi. and 290 pp. (33 figs.). See also Amer. Naturalist, xlii. 

 (1908) pp. 207-10. 



