THE SYSTEM OF ITIVI. L01TÎORIN.E. 



5 5 



notch corresponding to the canals of the smaller tentacles. In the 

 paired radial segments the broader half is always dorsal to the 

 narrower. The unpaired midventral radial segment is congruent in 

 form with the segments of the right side, that is to say, the broad er 

 half of it lies to the right of the narrower (textfig. i). 



The manner of branching of tentacular canals, as made out from 

 serial sections through pharyngeal mass of several specimens, seems 

 to be as follows : — 



Each radial canal, or the " main canal " as ThÉEL has called 

 it [45, p. 135]. gives off alternately four tentacular canals (textfig. 1). 

 The first tentacular canal branches out dorsad in paired radii, and to 

 the right in the midventral radius. The second arises on the opposite 

 side at a point just slightly anterior to the point where the first is 

 given off, directed ventrad in paired radii but to the left in the 

 midventral radius. These two canals run nearly transversely, and 

 approaching the margin of radial segments, open each into an ex- 

 panded part of the tentacular canal by a narrow orifice guarded by 

 the ventilative apparatus or " semilunar valves " in a manner similar 

 to that described for Cucumaria piatici (Brandt) by HÉROUARD 

 [15, pp. 580 — 583]. That expanded part of the canals communicates 

 with the large tentacles (D lf V 1 , Rj and L/), and is interposed 

 between a radial segment and an adjoining interradial segment. The 

 third branch, which is smaller than the two preceding and supplies 

 the medium-sized tentacles (D 2 and R 2 ), leaves the radial canal a 

 short distance anterior to the point where the second canal branches 

 out. In paired radii this stands dorsal to, and in the midventral 

 radius to the right of, the respective radial canal. The fourth, which 

 is the smallest of the four branches, is given off a very short distance 

 from the third branch on the opposite side. This supplies the 

 smallest tentacles forming the inner circle (V 2 and L 2 ). The third 

 and the fourth branches run forwards, each with the ventilative 

 apparatus in its course, over the incisions in the anterior margin of 



