COLOR CHANGES IN ANIMALS — CARLISLE 425 



develop a red tail at dusk. This can be shown to depend in no way 

 upon visual stimulation and to be mediated via tlie neurosecretory 

 center in the hind part of the brain, not via the centers associated with 

 visual input. 



The ability to change color gives the animal the best of several 

 worlds. It can stay hidden from its enemies or prey and yet be able to 

 display visual signals when needed. It can use color and pattern in 

 sexual display, and yet not fear discovery from the prominence of 

 these colors when they are not in use. It can, like the cuttlefish, use 

 color change as a scaring device or, like the squid, use it to lay a false 

 trail. I have seen a squid pursued and slowly becoming darker, as it 

 failed to throw off its pursuer until it was almost jet black. Suddenly 

 it shot out a jet of ink, blowmg it forward in the direction it was swim- 

 ming as a cigar shape about its own size. Simultaneously the squid 

 changed color becoming pale and almost transparent, and shot off at 

 right angles to its original course. Its pursuer continued after the 

 dark shape which was drifting along the original course while the 

 pale squid swam quietly away in a different direction. The ink of the 

 squid is no smokescreen as it is usually thought, but a decoy, much 

 more like the original dark squid than the suddenly pale squid it has 

 now become. 



