TUNICATA. 



99 



colonies, which attain a length of nearly three feet. One end is 



attached, the rest of the colony apparently lying along the sea- 

 bottom. 



Amaroucium roseum from Xaples forms translucent gelatinous 



masses ; a slice is exhibited, showing the long slender ascidiozooids 



immersed in the mass. 



Pharyngodidyon mirahile (Fig. 18 C), from 1600 fathoms in the 



Southern Indian Ocean, resembles a small mushroom, and is about 



one inch in height. This species is one of 



the few deep-sea Compound Ascidians. 



Leptoclimmi alhidum is a common and 



widely distributed species ; it occurs in the 



form of thin white crusts. The glistening 



white appearance is due to the common test 



being densely crowded with minute stellate 

 spicules of carbonate of lime. 



The specimen of Leptoclinum nejledum 

 (Fig. 18 B) encrusts a fragment of sponge. 



Goodsiria pedunculata from the Straits of 

 Magellan, forms a rounded cartilaginous mass 

 attached by a short peduncle ; sometimes 

 several masses are attached to each other. 

 Each of the small dark oval areas on the 

 surface corresponds to the branchial and 

 atrial orifices of one ascidiozooid. 



Sub-order 3. — Ascid^ Salpifoemes. 



The Salpiform Ascidians comprise only 

 one genus, Pyrosoma, which occm's in the 

 form of free-swimming colonies shaped like 

 hollow cylinders closed and rounded at one 

 end and open and truncate at the other 

 (Fig. 19). The wall of the cylinder is formed 

 of a single layer of ascidiozooids (Fig. 20), 

 so arranged that all the atrial orifices open 

 into the interior of the cylinder, and all the 

 branchial orifices on the exterior, the two 

 kinds of orifices being at opposite ends of 

 the body, and not close together, as in most 

 Ascidians. 



Pyrosoma elegans, natural 

 size. A. Side view of 

 entire colony. B. End 

 view of open extremity. 

 (Herdmau : Tunicata, 



Encyclopaedia Britannica.) 



simple and compound 

 E 2 



