56 HUBERT LYMAN CLARK ON 



widely distributed throughout the eastern Atlantic ocean, wherever suitable conditions 

 are found. In Jamaica, however, the species is extremely local and was found in only 

 one place, the so-called " lakes " at Port Royal. These " lakes " are parts of the harbor 

 which have been wholly or in part cut off by the growth of mangroves, so that they are 

 very quiet bodies of water, though not at all stagnant or brackish. On the roots of the 

 mangroves, which hang down in the water on all sides, is an abundant growth of 

 vegetable and animal life. In some places, a particular sea-weed, one of the Florideae, 

 crowds out all the other Algae. In this weed Synapta vivipara makes its home, and though 

 carefully looked for elsewhere, it was found in numbers only in such situations. The 

 late Dr. J. E. Humphrey kindly identified this alga for me, as Acanthophora thierii 

 Lamouroux. This weed also grows in large bunches on the bottom in the shallow water 

 of the harbor just outside the " lakes,'' and I was told that in 1893 the Synapta was 

 found in great quantities there, but in 1896 it seemed to have entirely disappeared 

 from that place. At Montego Bay, on the northwest coast of Jamaica, Acanthophora is 

 very abundant on the mangrove roots, but a thorough search revealed no sign of 

 Synaptas there. Even in the Port Royal "lakes," their distribution was very capricious, 

 and only certain favored masses of Acanthophora contained them in any numbers. They 

 seem to be quite social in their habits, and usually if one or two were found, there would 

 be a whole colony of them. They are very sensitive to changed conditions, and I was 

 unable to keep them alive in aquaria more than twenty-four hours. The anchors in the 

 body-wall are so abundant and prominent that they cling very tenaciously to anything 

 with which they come in contact, especially the hands, and it is accordingly no easy task 

 to disentangle them from the sea-weed without injury. They seem to be able to swim 

 very little, and it is doubtful if they ever leave the bunch of sea-weed, in which they 

 have once settled. Their food consists largely of vegetable matter, diatoms being 

 abundant in the stomach, but probably many small crustaceans and worms are also eaten. 

 The tentacles are kept constantly in motion, and it was very common to find small 

 amphipods caught among them, but I was unable to find evidence that these crustaceans 

 ever served as food. Semon ('87) has called attention to what he considers a mimicry 

 of coloration in Synapta inhaemns, in relation to the bottom on which it is found. In 

 this connection, it is interesting to note that the reddish and greenish brown shades 

 of S. vivipara are almost exactly those of the Acanthophora in which it lives. So close 

 is the resemblance that it is very easy to overlook Synaptas, even when the sea-weed is 

 in one's hand. Whether this coloration is actually protective or not is doubtful, for they 

 seem to have few, if any, enemies. No internal parasites were observed ; externally 

 however a small brown calcareous sponge, like Grantia, was found firmly attached 



