182 



LOWER INVERTEBRATES. 



s^M, 



t^^. 



3!.r. 



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

 trees divide ut once into two very bushy branches, and the Cuvierian tubes foini a 



brush-like tuft about an inch in 

 length. 



iJladodactijla crocea was found 

 p^ , J adhering to the huge tangle in 

 'c,^, the southern seas, and is abun- 

 dant at the Falkland Isles. It is 

 of a bright saffron color. The 

 three anterior anibulacral vessels 

 are near together, and bear num- 

 erous well-developed sucking-feet 

 for locomotion, while the two am- 

 bulacra of the biviinn are also 

 near together on the back. In 

 the females these latter ambula- 

 cra have very short, tentacular 

 feet, which, though provided 

 \\ith sucking discs, seem, from 

 the rudimentary condition of the 

 rosette of calcareous plates at 

 their tip, scarcely fitted foi- loco- 

 motion. In the males there is 

 rather less difference between the 

 ilorsal and ventral ambulacra. 

 In the females the young were 

 found closely packed in two con- 

 tinuous fringes adhering to the 

 water-feet of the doi'sal ambula- 

 cra. " Some of the mothers with 

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

 bodies entirely hidden l)y 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 e.\j)anded 

 crown of oral tentacles." 



In the AspidochirotiB, or holothurinns with disc or shield-shaped tentacles fur- 

 nished with tentacular ampullse, the left resjiiratory tree is bound to the body-walls, 

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

 These are tlie highest type of Ilolothuroidea, and are mainly trojiical in their dis- 

 tribution. 



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

 less quadrilateral in section, and the ambulacral feet project from paj)illa,'. Three 

 distinct rows of these can usually be traced ujjon the flat ventral surface. *S'. varie- 

 ffati/s, which has been found .at the Samoan Islands, and at the Philip])ines, attains an 

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

 been taken. 



Mulleria has five calcareous ])lates or teeth at the anal extremity. 

 In the ty]jical genus Ifolothuria the feet are scattered .all over the surface of the 

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



Fio. KO. — Psoitis fall 



