98 
SHELL GALLERY. 
resembles an elongated head of clover on a thickened stalk. The 
individuals which compose the head are arranged in spiral lines, 
Fig. 17. 
A. Botryllus violaceus, magnified, showing two systems of 6 and 7 ascidiozooids. 
B. One ascidiozooid extracted. 
a, branchial ; b, atrial orifices ; c, branchial sac ; d, stomach. 
(After H. Milne-Edwards.) 
the atrial orifice of each ascidiozooid opening separately and not 
into a common cloaca. 
Colella quoyi (Fig. 18 A), from 25 fathoms off Kerguelen Island, 
forms a rounded head on a short peduncle, the total height being 
Fig. 18. 
Colonies of Ascidise composite, natural size. A. Colella quoyi. B. Leptoclinum 
neglectum. C. Pharyngodictyon mirabile. D. Botryllus. 
(After Herdman, Challenger Report and Encyclopeedia Britannica.) 
one inch. The ascidiozooids are arranged in vertical lines in the 
" head," each line consisting of a double zigzag series. 
JuUnia ignota, from the Antarctic regions, forms long narrow 
