182 



LOWER INVERTEBRATES. 



tentacles can be deeply retracted. There are three Polian vesicles, the respiratory- 

 trees divide at once into two very bushy branches, and the Cuvierian tubes foi-m a 



brush-like tuft about an inch in 

 wMa,-.^^ .sAS«j4 ALaI .. length. 



Cladodactyla crocea was found 

 adhering to the huge tangle in 

 the southern seas, and is abun- 

 dant at the Falkland Isles. It is 

 of a bright saffron color. The 

 three anterior ambulacral vessels 

 are near together, and bear num- 

 erous well-developed sucking-feet 

 for locomotion, while the two am- 

 bulacra of the bivium are also 

 near together on the back. In 

 the females these latter ambula- 

 cra have very short, tentacular 

 feet, which, though provided 

 with sucking discs, seem, from 

 the rudimentary condition of the 

 rosette of calcareous plates at 

 their tip, scarcely fitted f oj- loco- 

 motion. In the males there is 

 rather less difference between the 

 dorsal and ventral ambulacra. 

 In the females the young were 

 found closely packed in two con- 

 tinuous fringes adhering to the 

 water-feet of the dorsal ambula- 

 cra. " Some of the mothers with 

 older families," says Sir Wyville Thomson, " had a most grotesque appearance, — their 

 bodies entirely hidden by the couple of rows, of a dozen or so each, of yellow vesicles 

 like ripe, yellow plums ranged along their backs, each surmounted by its expanded 

 crown of oral tentacles." 



In the Aspidochirotse, or holothurians with disc or shield-shaped tentacles fur- 

 nished with tentacular ampullae, the left respiratory tree is bound to the body-walls, 

 there are no retractor muscles to the pharynx, and Cuvierian organs are present. 

 These are the highest type of Holothuroidea, and are mainly tropical in their dis- 

 tribution. 



In Stichopus the tentacles are eighteen or twenty in number, the body is more or 

 less quadrilateral in section, and the ambulacral feet project from papilljE. Three 

 distinct rows of these can usually be traced upon the fiat ventral surface. S. varie- 

 gatus, which has been found at the Samoan Islands, and at the Philippines, attains an 

 enormous size. Examples three feet or more in length, and eight inches thick, have 

 been taken. 



Mulhria has five calcareous plates or teeth at the anal extremity. 

 In the typical genus Holothiiria the feet are scattered all over the surface of the 

 body, usually without distinction into rows. Some of the species attain large dimen- 



FlG. 160. 



-Psoitis fabricii, showing under surface with tliree rows 

 of ambulacra. 



