AMPHIBIAN MIGRATION. 



Table II. 



11 



The veal cause of the Kewts normally walking downhill may- 

 lie in the weakness of the limbs. Yet, from a few observations 

 ma<le on the strong-limbed Toad placed horizontally on an incline, 

 I am induced to think that it also usually goes down, if given 

 the choice. But, as in the case of the Newt, the cause of this ' 

 behaviour of the Toad when placed horizontcdly on an incline 

 receives a simple mechanical explanation. The kick given by the 

 liind leg, which is higher up the incline than the other, ^vould 

 naturally tend at the moment of the hop to turn the animal down- 

 wards. The Toad always hops downhill, but it crawls and rarely 

 hops up a gradient. On an incline of 12^^ one of my Toads would 

 begin hopping downhill. If it was then teased on one side so as 

 to send it up, the Toad would endeavour to continue hopping 

 uphill, but when once facing up, the gait very quickly changed 

 to a crawl. It may be observed that when endeavouring to hop 

 up, the hind limbs cannot be brought up vnider the body from a 

 state of extension unless they scrape the ground. After they have 

 once scraped the ground in this way, the Toad ceases to attempt 

 to hop, but crawls. It would appear-, therefore, antecedently 

 probable that in the spring, at the time of their greatest activity, 

 the genei'al tendency of the Toad also would be downhill towards 

 water, rather than up. 



One more observation is worth recording. Some Newts, when 

 placed on a level surface or on only a slight incline, would never 

 start oft' straight in any direction. They always turned, and some 

 of their turns were very elaborate. They would meander about 

 the centre of the board around and up and down, before setting 

 out in any particular direction. When once started, however, 

 they went ahead. I i-egard this elaborate turning merely as 

 a complex withdrawing response. Similar behaviour has been 

 noted in the Crayfish *. 



All those Newts which winter on the slopes around the pond 

 could, by their geotactic responses, easily find their way back to 

 the water in spring. They would simply walk downhill. 



* .1. Carlton Bell, " Reactions of the Crayfisl)," Harvard Psychological Studies, 

 Vol. ii. 1906, p. 61o. 



