BREATHING STRAINS 267 



Crustacea the gill-plumes are large and lax, the gill- 

 chambers swollen, and the openings leading to and 

 from the gill-chambers singularly patulous. These 

 modifications are most apparent in the active prawns 

 and crabs which live near the loo-fathorn line : Ence- 

 phaloides armstrongi (Fig. 6i), a spider-crab found on 

 the edge of the abyssal slope all round the coasts of 

 India, exhibits them in an extreme degree, and in this 

 species the enormous gill-chambers rise up until they 

 meet across the middle line of the carapace, but with- 

 out any fusion of their walls. Such a remarkable 

 increase in the breathing capacity appears to point, 

 like the chest-expansion of mountaineers, to difficulties 

 of respiration of some kind to be surmounted. 



Although the conditions of life in the depths 

 might seem to be reduced to a minimum of simplicity, 

 yet evidences are not wanting that, among the higher 

 Crustacea there, they are complicated, much as they 

 are everywhere else, by the play of the sexual 

 instincts. 



It is written that the male must exert himself to 

 find a mate, and where sight cannot help him in his 

 search a kind of blind-man's buff is the only alter- 

 native. In this serious game many deep-sea Crustacea 

 especially those of the shrimp tribes (Caridea), trust 

 to the sense of smell, as the greatly-developed outer 

 or olfactory branch of the first pair of antennae bears 

 witness. These antennae, again, seem to be used by 



