398 THE INFLUENCE OF LIVING SURROUNDINGS. 



Moreover, there are very many instances of similarity of 

 colouring between two creatures very remote from each other, 

 and in which it is very difficult to discover any relations 

 between the two animals thus characterised. Thus, many 

 Annelida, Mollusca, Planariae, and Ophiuridse live on the stocks 

 of the keratose corals, which they resemble greatly in colouring 

 though not in form. In the same way all sorts of creatures 

 may be found, on the disks of star-fish and Comatulse or on the 

 spherical shells of Echinidse, which have perfectly assumed the 

 colour of the animal on which they live. Here, certainly, we 

 cannot speak of mimicry in the strict sense ; it is far more pro- 

 bable that this resemblance serves only to enable these creatures 

 to escape detection, living, as they do, exposed to a certain 

 degree of danger on the surface of others. But, in the case I 

 shall now describe, it appears to me that it can be of no use 

 even in this way. 



Together with Xesta Cumingii a second species of the same 

 genus lives in Mindanao which differs quite as much from Xesta 

 Cumingii as this species does from those inhabiting Java or the 

 Moluccas. On the other hand, its shell looks exactly like those 

 of the species of Rhysota, a genus in the highest degree charac- 

 teristic of the Philippines (see fig. 105, a). These have shells 

 of a uniform brown colour, often wrinkled and somewhat 

 depressed, and not overlapped at all by any marginal develop- 

 ment of the body the lobes of the mantle. The foot is Hat, 

 broad and short, and bears at the end a gaping gland. All the 

 species of Rhysota live on the ground under trees ; and when, 

 on particularly damp days, they quit the ground, they never 

 climb trees, but only low plants growing in deep shade. It was 

 from its sharing these characteristics that I regarded the new 

 Xesta which I called Xesta mindanacnsis, from the locality 

 where it exclusively occurs as being a true Rhysota till I had 

 the opportunity of examining it anatomically, 



Xesta mindanaensis and Xesta Cumingii are the only two 

 species of this Indian genus that are widely distributed in the 

 Philippines ; the latter is found from Mindanao as far as Bohol 

 and the southern part of Leyte ; the former occurs exclusively 

 in Mindanao, the southern island. But while their nearest 



