46 , DR. R. V. WILLEMOES-SUHM ON SOME ATLANTIC 



V. On the Development of a Land-crab. 

 (Plate XI. figs. 1-3.) 



In most books on natural history we find concerning the land-crabs a remark that, 

 according to Mr. West-wood's observations, they migrate to the sea when the time for de- 

 positing their eggs has come, and that the young ones, when coming out, have the same 

 form as their parents. The same thing is to be observed in Astacus fluviatilis ; and the 

 knowledge of these two facts has been much in the way of the general acceptance of 

 Mr. Vaughan Thompson's first observations on the Zoea-stages of crabs. Also his state- 

 that he found Zoea-brood in the eggs of a Gecarcinus has been doubted ; for, according to 

 Fritz Miiller*, Mr. Bell considered himself justified in eliminating Thompson's observa- 

 tion, because he could only have examined ovigerous females preserved in alcohol. The 

 following lines, however, will show that there is no reason to doubt Mr. Thompson's 

 statement. Fritz Miiller himself, though we owe him many observations on land-crabs, 

 says only that there is Zoea-brood in Ocypoda and Gelasimus, but had no occasion to 

 observe the Gecarcinoids. 



Watching the habits of these crabs is always attended with some difficulties, as most 

 of them are nocturnal. In St. Thomas I only succeeded in getting a few Gelasimi. 

 Only in the Bermudas did we get Gecarcinoids : — the large Cardisoma guanhumi, 

 which was caught by torch-light in the interior of the island, but all the specimens we 

 got were males ; besides, Mr. Moseley caught Gecarcinus lateralis and Ocypoda rhombea, 

 and I myself caught several crabs allied to Boscia. I watched there also for a long time 

 the lively Grapsus cruentatus, which lives in great quantities in Hungry Bay, among the 

 mangrove trees. It has entirely taken to terrestrial habits, makes deep holes and runs up 

 and down the mangrove trees. The holes, however, it always makes so near the shore, 

 that it is sure to find water at a depth of 2 or 3 feet. What its mode of development 

 is I could not find out, as it was evidently not their breeding-season (June). Arriving 

 in the beginning of August at the Cape-Verd Islands, I found in St. Vincent many holes 

 on shore inhabited by Ocypoda hippeus, a crab running with marvellous velocity over the 

 sand, and very valuable to me, as it gave me ample opportunity of studying the interest- 

 ing entrance to the branchial cavity described by Fritz Miiller. But also in these I could 

 discover no trace of eggs or of young. Holes made by the same crab we found 

 again in the island of San Jago, where they are to be seen in abundance near the 

 houses of the little village which surrounds the old cathedral of Bibiera Grande. But 

 besides Ocypoda hippeus, we got in San Jago another large land-crab, caught by Mr. 

 Moseley's seining-party at night in the bay of Porto Praya, a true Gecarcinoid, be- 

 longing to the same genus (Cardisoma) to which the Bermuda ones belonged. Unfor- 

 tunately I cannot make out its specific name, as it is not mentioned in Milne-Edwards's 

 ' Histoire Naturelle des Crustaces ' t ; but I suppose it is an animal well known to Euro- 

 pean carcinologists as inhabiting the Cape-Verd Islands, and, very likely, also the coast 



* ' Facts and Arguments for Darwin,' by Fritz Miiller (translated by W. S. Dallas. London : 1869), p. 48. 

 t Probably described in the same author's ' Crustaces des iles du Cap Vert.' 



