IQ Dr. Asajiro Oka : 



the remaining eight are only half as long as the longest ones. Two 

 of the longest tentacles are placed in the median plane of the zooid, 

 the other two making right angles with them. At the level of 

 their attachment a sphincter composed of loose circular muscle 

 fibres encircles the base of the branchial siphon (PL II., figs. 9 & 

 10). 



Each tentacle is attached separately and has a round tapering 



and generally curved stem and a rather blunt apex. The wall of 

 tentacle is formed externally by an epithelium of flattened or 

 cubical cells and is nowhere ciliated. The interior of the tentacle 

 is filled with the homogeneous matrix of connective tissue with 

 some scattered cells. A few delicate longitudinal muscle fibres are 

 sometimes distinguishable under the epithelial layer. Whether 

 the blood spaces are continued into the interior of the tentacles, 

 though very probable, could not be ascertained. 



Periphanjngeal hand. In the present species the peripharyn- 

 geal band is remarkably well developed, resembling in many 

 respects that of simple ascidians. It consists of two parts, a thin 

 membrane and a ciliated ridge (PL IL, fig. 9, piyh. m., prph. r.) 

 For the greater part of their course they run close to and parallel 

 with each other, forming between themselves a narrow groove, the 

 "gouttière péricoronale " of French authors. They encircle the 

 top of the branchial sac at a short distance from the bases of 

 tentacles. The peripharyngeal membrane, called the " Ring- 

 falte ' ' b}^ German writers, is a thin membrane of nearly equal 

 breadth throughout, and is composed of flattened cells without 

 cilia. At the ventral median line the membranes of both sides 

 meet each other at the pointed anterior extremity of the endostyle. 

 Dorsally the membrane reaches the dorsal tubercle where it is 

 continued for some distance along the lateral region of that organ 

 (PI. II., fig. 11, j)rp]i. m.). Throughout its whole extent the 

 breadth of the peripharyngeal membrane is about equal to the 

 height of the ciliated ridge forming the other lip of the groove. 



The peripharyngeal ridge is composed of a band of ciliated 

 epithelium running parallel with the peripharyngeal membrane on 

 its posterior side. It is connected at its ventral and dorsal ends 



