REPORT ON THE CRUSTACEA MACRURA. lxxxix 



damaged specimeu of what I have described as Caridina typus, Milne-Edwards, but 

 which I am much inclined to think from its immature condition is the young of the 

 Atya suloatipes that exists in the same locality. 



In form these animals have a very peculiar feature in the articulation of the heavy 

 chelate joint of the first two pairs of pereiopoda, which has been described at pp. 6 and 

 7 of this Report and by Dr. Fritz Miiller. 1 When the hand is opened, according to 

 Fritz Miiller, the hairs upon the margin of the fingers spread like a fan, gather and 

 retain fine mud ; when the hand is closed these hairs close round the mud and com- 

 press it into a pellet which is passed into the mouth, and so the animal lives on the 

 small organic substances that exist in the mud, which it collects with great rapidity. 



These animals, of which the male is smaller than the female, as is frequently the case 

 when they are not provided with offensive weapons, are only known to inhabit fresh water, 

 and singular to relate, although they are inhabitants of distant localities, several of 

 which are oceanie islands,' yet all the species bear so close an affinity of form that it is 

 difficult to determine one from the other by any permanent character. 



The question naturally arises how, so far asunder as the habitats of these animals are, 

 can they be brought to live without any intermediate connecting influence as far as we 

 can determine ? 



Mr. Darwin, in his book on Earthworms, says that in every bit of land or distant 

 island worms are found in the soil ; considering that they are land and air-breathing 

 animals, it is a matter of curious interest to determine how they get where they are. 



M. A. Certes, in the Comptes rendus, says that having taken carefully collected 

 sediment from which he evaporated the water, he three years afterwards treated the 

 residue with boiled and filtered rain-water. All care .having been taken to keep out 

 germs from the air, after two months a Nauplius-like form was detected which later on 

 took the form of Artemia salina. M, Certes points out that in cases of this kind death 

 was only apparent, and that organic conditions and nutritive changes do not cease 

 entirely. Thus it appears that it is quite possible for wading birds to be the means of 

 carrying mud containing either animals or ova to a considerable distance and so trans- 

 ferring species to a great distance from one locality to another. 



One of the most abundant in specific forms is the genus Alplieus, including those 

 subgenera that are separated more for the convenience of classification than from any 

 distinguishing point of more than specific value, Paralpheus, Synalpheus, Cheirothryx, 

 and Bet&us. These contain about eighty different species, and with the exception of a 

 single instance they have all been taken within 52 fathoms from the surface. They are 

 mostly recorded from muddy bottoms, but they are frequently found sheltered among 

 Corallines and masses of Sponges. From their frequently being found in ooze and 

 muddy bottoms I am inclined to believe that they burrow more decidedly than is the 



1 Kosmoa, vol. ix. pp. 117-124, 1881. 



(ZOOL. CHALL. EXP, — PART LII. — 1888.) Eff 111 



