vi FAMILIES OF CATOMETOPA 195 



astonishing rapidity, and they seem to l>e always on tin- alert,. 

 directing their eyes, which are placed on exceedingly lonu stalks, 

 in all directions. 



Some of the Grapsidae, e.g. Aratus pisonii, arc partially 

 adapted.for life on land. Fritz Miiller, in his Facts for Darwin, 

 alludes to this creature as "a charming lively crab which 

 ascends mangrove bushes and gnaws their leaves." The carapace 

 can be elevated and depressed posteriorly, apparently by means 

 of a membranous sac, which can be inflated by the body-fluids. 

 This Crab retains its gills and can breathe under water in the 

 ordinary way. 



A great many other Catometopa are land-oral >s; but we may 

 specially mention the genus Gecarcimts, related to the marine 

 Grapsidae, which has representatives in the West Indies ,-iml 

 West Africa. The Crabs of this genus may live in sheltered 

 situations several miles from the sea, but in spring the whole 

 adult population rushes down in immense troops to the slum-, 

 where breeding and spawning take place ; and when this is 

 completed they migrate back again to the land. The young pass 

 through the normal larval stages in the sea and then migrate 

 inland. 1 



Fam. 1. Carcinoplacidae.- -The carapace is rounded and 

 broader than long, usually with toothed front margin. The 

 orbits and eyes are normal, and not much enlarged, flcri/oii, in 

 the deep littoral of the northern hemisphere. A'///'///^", J'm/n- 

 jilii.i'., etc., in the American coastal waters. 7 //_/>// /<"///// /'x, etc., 

 in the Indo-Pacific. 



Fam. 2. Gonoplacidae. The carapace is square, \\iili the 

 antero-lateral corners produced into spines. The orbits are 

 transversely widened, and the eye-stalks long. Gonpplax, widely 

 distributed in the littoral zone. (!. r}iinl>i<l>'x in I'.ritisli and 

 Kuropeaii seas. 



Fam. 3. Pinnotheridae. Carapace round, with mdi>iinct 



front, al margin. Orbits and eyes very small, often rudimeniai \ . 

 The members of this family li\e symbolically or paia-ii icalh 

 in the shells of liying I'.ivaKe Molluscs, corals and worm- 

 tubes in all seas except the Arctic. /'/'// nutlu'i-i-x i>ixinii i- I'airly 



Tlirl'i' :ij>]ic;irs t" lie snlllr ilnlllil on till-, ]>ciilil, as \\'rst \\ HIM 1 SC6 | '. 



ilrsi-rilii'i] direct df\ ' li.]niicnt in ;> Gecardnus. Possibly differenl 

 variously. 



