HIDDEN LINKS 151 



organs of touch, since the eyes of Psalidopus are very 

 small, and are quite devoid of facets and pigment, and 

 so can be of no use for distinct vision, even if they 

 are sufficient for the discrimination of light from 

 darkness. 



A third noteworthy crustacean dredged upon this 

 occasion was a hermit-crab i^Parapylocheles scorpio), in 

 which the body is as symmetrical as that of a lobster. 

 In most hermit-crabs the abdomen or ''tail" is soft, 

 and has a spiral twist, and the abdominal legs are 

 present on one side only ; but in Parapylocheles (as 

 in the rare genera Pylocheles, Pomatocheles, Mixto- 

 pagu7'7ts, Xylopagurus, and Glaitcothoe) the abdomen 

 is perfectly straight, and is soft only on its under 

 surface, and has the proper number of legs on both 

 sides. All these forms are, in fact, connecting 

 links between the lobsters and the typical hermit- 

 crabs, and are specially interesting on that account. 

 In Parapylocheles scorpio the eyes, though somewhat 

 pallid and extremely small, are properly formed, and 

 are probably of some slight service to the animal. 



After heaving - in the trawl, we passed through 

 Manners Strait into the Bay of Bengal, and I then 

 had the mortification of passing South Sentinel Island 

 — the only Indian home, unless the Nicobars be 

 included in India, of the robber land-crab [Birgtt^s 

 latro) — without being able to land there. I was particu- 

 larly anxious to spend a few hours on the island in 



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