TUNICATA. 339 



The young BoUenlae sometimes grow on the stem of the parent. The 

 branchial orifice is nearest the stalk, but as the body is pendulous it becomes 

 higher than the other opening, as usual amongst the ascidians. (Rupert 

 Joues.) B remformis, iSlc L. lives attached to stones in deep water ; it is 

 sometimes brought up by the fishing hooks. ( Gould.) Elizabeth harbour, 

 70fms. {Ross.) 



Dlsir. N. Zealand ; Greenland, {B. ovifera—y oYiiceW?^, L.) Mass. U. S. 



Suh-gemis f Cystingia (Griffithi) Mc Leay, 1824. Arctic seas, Felix 

 harbour and Fox's ohanuel. Test sub-coriaceous, anal orifice irregular, 

 terminal. 



FAMILY II. Clavellinidae. Social Ascidians. 



Animal compound, fixed ; individuals connected by creeping tubular pro- 

 longations of the common tunic, through which the blood circulates, (or by 

 a common gelatinous base). 



These small or microscoj^ic creatures are found on stones, shells and sea- 

 weed, adhering by numerous root-like projections of their outer tunic. They 

 are so transparent and colourless that they may be examined without dissec- 

 tion (PI. 24, figs. 6, 7). The position of the stomach is indicated by an 

 orange-coloured spot; the oesophagus is long, and the intestine returns 

 parallel to it. The heart and ovary are near the stomach. The gill, perfo- 

 rated by rows of holes, completely separates the branchial cavity from the 

 cloaca ; a series of membranous processes {lancjuettes) project from its ueural 

 side. The creei^ing tube contains two channels through which the blood 

 circulates in opposite directions. 



Eeproduction is effected by ova and by buds produced on filaments given 

 off by the creeping tube. These off-shoots are hollow, and liued by a mem- 

 brane continuous with the inner tunic of the ascidian ; the circulation passes 

 into them and they grow and branch and form buds containing little organized 

 masses from which the internal organs are gradually developed. The bran- 

 chial sac is perfectly outlined before it communicates with the interior, and the 

 curved digestive tube is seen before the oral opening is formed. The new 

 individual may continue united with the parent, or become completely free 

 by the rupture of the connecting tube. {Milne-EdvMrds.) 



Clavellina, Sav. 



Etijm. Clavella, a small staff, Syn. ? Rhopalaea, Phi. 



Tyiw, C. Icpadiformis, PI. 24, fig. 6. 



Body elongated, erect, more or less pedunculated; test smooth and 

 transparent ; orifices without rays ; thoracic region usually marked with 

 coloured lines. 



Bistr. Greenland, Brit. Medit. On rocks and stones at low-water. 



a 3 



