3H 



ECHINO DEEMS. 



breaking 

 a part of 



\ 



up their tissues; while others have an objectionable habit of shooting out 

 their intestines in long viscous strings ; and it is owing to this that a 



common British form has gained 



the name cotton-spinner. It has 



been suggested that this habit has 



been acquired in connection with 



the presence in the intestine of 



small parasites, and these in their 



turn have their habits affected 



according as they live in holo- 



thurians 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. 438 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 beche-de-mer, 



as the holothurians are called by 



the Portuguese, takes place very 



largely 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. 



CLUB-LIKE SEA-CUCUMBER (Rhopalo- 



dina) (nat. size). 



V DEEP-SEA HOLOTHURIAN, 



Psychropotes (§ nat. size). 



Development of Echinoderms 



Few things about echinoderms are more remarkable 

 than their modes of reproduction, which include both a 

 sexual method, from the fertilised 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 



A PLATED HOLOTHURIAN (Psolus). 



Some plates of the back, above 

 the brood-pouch, are removed 

 (enlarged 3 times). 



