HOLOTHURIANS OR SEA-SLUGS. 45 



in the integument ; there are five retractor muscles for the 

 tentacles, and branched lungs. 



Several species of Cacumaria are found in the British Seas, 

 but one only is of large size ; that is the sausage-shaped creature 

 which E. Forbes called the Great Sea-cucumber {Cucumaria 

 frondosa) and the Tangle Sea-cucumber (C fucicola), in his 

 well-known work, these being synonymous terms. This species 

 has been found as far north as Greenland, and lives in North 

 American as well as North European waters. Dr. William 

 Stimpson, the well-known American naturalist, states that it 

 makes very palatable soup. 



The first change from the typical Cacumaria is seen in the 

 modification of the tentacles, one pair of which becomes smaller 

 than the other four ; this is to be observed in some species of 

 Cucumaria itself. The next step is the scattering of the suckers, 

 which are no longer confined to the lines of the rays, but 

 distributed apparently irregularly over the whole of the body ; 

 this also is found in what some naturalists still call Cucumaria, 

 though Dr. Lampert the author of a recent monograph of the 

 group, has proposed for such Sea-cucumbers the new generic 

 term of Semperia* — a name given, it need hardly be said, 

 in honour of the distinguished professor of Wiirzburg, who 

 during his now classical travels in the Philippines devoted much 

 attention to the Holothurians ; in our own seas the common 

 Thy one {Thy one impillosa) is an excellent example of a form in 

 which the suckers are scattered over the whole body, or take on 

 what systematists call a sporadipod arrangement. 



In another set of forms the integument becomes very heavily 

 armed with calcareous plates, and the body is consequently 

 always of the same form, and not variable like the Great Sea- 

 cucumber. The Sea-girkin {Genus lacteus and 0. hrunneus of 

 Forbes being synonymous terms) is one good example of this ; 

 another is presented by the Snail Sea-cucumbers (members of 

 the genus Psolus), though here the species vary a good deal in 

 the extent of their armature, the circumpolar P. fahricii being 

 much richer in large plates than the P. phantapus which is 

 found in our own seas. Another remarkable peculiarity in 



■■' New, that is, for Holothurians ; it has long been used amongst 

 Mollusca, and if the generic division be allowed to stand, it must be altered 

 for Echinoderms. 



