HOLOTHUEIANS OR SEA-SLUGS. 47 



metrical as many worms ; they still, however, have calcareous 

 deposits in their integument; Chirodota, an allied genus, having 

 little rounded structures which look like toothed wheels, and 

 Synapta, having fenestrated plates to which a projecting anchor- 

 shaped spicule is attached ; it is to the projecting ends of these 

 anchors that the skin of Synapta owes its peculiar roughness. 

 Though larger than Chirodota, Synajyta never reaches in our 

 own seas to the size of more than a few inches, but in the 

 tropical seas the species of this genus may attain to a great 

 length, being even as much as seven feet long. Synapta is 

 remarkable among Echinoderms for having the sexes united. 



A group of curiously modified Holothurians have been made 

 known by the recent explorations in deep water, but as the 

 Elasipoda are confined to great depths, and an enumeration of 

 their characteristics would obscure these leading facts in Holo- 

 thurian organisation which it is the purpose of this paper to 

 describe, we must postpone any notice of them to another 

 occasion. 



During the last few months some of the more leading types 

 of Holothurians have been set out in spirit for exhibition in the 

 Starfish Gallery of the British Museum (Natural History). 

 What are to be seen there are such forms as every reader of 

 ' The Zoologist ' ought to know a little about, but they do not, 

 of course, give any idea of the extent of the National Collection 

 of these animals. Comparatively rich as that collection is, 

 it is certain that it still wants a number of described forms, and 

 that there are still many Holothurians in the sea which have 

 never yet been named or described. If this little paper should 

 excite the interest of any reader in these instructive and incom- 

 pletely known animals he may give a proof thereof by devoting 

 his leisure to their collection ; in justice, however, it must be 

 said that the appearance of his preserved specimens will not 

 give the brilliant results that fall to the collector of birds or 

 insects. Holothurians have an irritating way of ejecting their 

 viscera or of breaking to pieces ; the best way, therefore, to kill 

 and preserve them is to plunge them at once into spirit ; before 

 the specimens are packed oft' and sent to the Museum it is well 

 to completely change this spirit, as it soon becomes weakened 

 by the quantity of water in the Sea-slug's body. 



