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. Botryllui violaceus, magnified, showing two systems of 6 and 7 ascidiozooids. 



B. One ascidiozooid extracted. 



a, brancliial ; h, 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. 



Oolonies of Ascidise compositse, natural size. A. Colella quoyi. B. Leptoclinum 

 neglectum. C. Pharyngodictyon mirabile. D. Botryllus. 



(After Herdman, Challenger Eeport and Encyclopaedia Britannica.) 



one inch. The ascidiozooids are arranged in vertical lines in the 

 " head," each line consisting of a double zigzag series. 



Julinia ignota, from the Antarctic regions, forms long narrow 



