3282 



ECHINODERMS 



habits affected according as they live in holothurians that are or are not cotton 

 spinners. Among the parasites of holothurians should specially be mentioned a 

 little fish of the genus Fierasfer, that inhabits the intestine of some species, and has 

 its food provided for it by the holothurian; this fish is described on p. 2810 of Vol. V. 

 Holothurians are of interest, as furnishing a food known as trepang, which 

 ranks with edible birds' nests among the delicacies of a Chinese table. The fishing 

 for trepang, or b$che-de-mer, as the holothurians are called by the Portuguese, takes 

 place very largel)' in Oriental countries, and is being extended to the barrier reef of 

 Australia. All kinds are not equally esteemed, for some have too much calcareous 

 deposit in their skin, and others get rid of their insides, and so become too lean. 



DEVELOPMENT OF ECHINODERMS 



Few things about echinoderms are more remarka'ble than their modes of repro- 

 duction, which include both a sexual method, from the fertilized egg, and also one 

 by budding or splitting of a single individual into two. Many echinoderms, as we 

 have already seen, have the curious power of breaking off portions of themselves, 

 as the brittle star or crinoid can break off their arms. Also they are able to eject 

 the whole or a part of their viscera, a faculty which has been specially developed in 



some of the holothurians. It is still 

 more remarkable that the portions so 

 broken off can be grown again, and 

 that they themselves can, in many 

 cases, grow fresh bodies, and become 

 complete individuals. A starfish of 

 the genus Linckia commonly avails 

 itself of this faculty; and it is by no 

 means rare to find big arms with a 

 small body at one end, and four little 

 arms growing out of it; these are 

 known as comet forms. This power 

 of reproduction is probably due to 

 the extension of all the systems of 

 the body into the arms; the arms of 

 brittle stars, which do not contain 

 all the systems of the body, have 

 not been known to reproduce indi- 

 viduals. In some cases echinoderms 

 have been seen definitely to repro- 

 duce themselves by fission or split- 

 ting in half. Such division is well 

 known to take place among the sea 

 cucumbers; and it is believed by 



GREEN SNAKE STAR. SOme to take P lace even in brittle 



(Enlarged five times.) stars; the specimens of the six- 



