PHOTOPHOBIA 31 



few more hours the rest of the snake was con- 

 sumed. 



Blood - sucking leeches prefer to feed under 

 cover and, when gorged, retreat to cover as 

 quickly as may be. A Ceylon land leech which 

 I was keeping under observation remained on 

 my arm for ten minutes without attempting to 

 puncture the skin, in a contracted, flushed, 

 quiescent posture. I then placed a silk handker- 

 chief over the waiting worm, with the result that 

 two minutes later a puncture was felt, and the 

 attachment continued for thirty - eight minutes. 

 When the leech was placed upon a dead leaf after 

 the meal it immediately crawled underneath. 



Apart from parasitism, the purest expression 

 of cryptotaxis is that which is manifested by 

 genuine cave-dwellers, and by animals which not 

 only burrow underground, but also find their 

 food underground, such as the mole - crickets 

 (Gryllotalpa 1 ), the earthworms and the creatures 

 which feed upon them, namely, moles, worm-eat- 

 ing slugs (Testacella), earth-snakes (Uropeltidce), 

 and apodous Batrachia (Cczciliida). I have kept 

 an Ichthyophis alive for ten months in one half 

 of a coconut shell covered over by the other 

 half, feeding it exclusively upon earthworms. 



The most primitive members of the phylum 

 Arthropoda are to a great extent cryptozoic ; in 

 Ceylon there is a species of the Thysanuran 



1 Gryllotalpa flies to artificial light. 



