RHEGMATODES TENUIS. 



Fig. 137. 



into the interior cavity ; the chymiferous tubes extending nearly to the 

 apex, leaving but a short digestive cavity, the edges of which scarcely 

 meet (Fig. 137), so that, when the actinostome is closed, the lips resem- 

 ble a piece of catgut tied by a string close to the end ; the marginal 



tentacles are long, gener- 

 ally carried extended, and 

 when contracted twist only 

 two or three times, and are 

 not carried tightly curled, 

 as in Zygodactyla ; the ova- 

 ries are very narrow, and 

 extend almost the whole 

 length of the chymiferous 

 tubes, from the upper mar- 

 gin of the digestive cav- 

 ity, to about one tenth the 

 length of the radiating tube 

 from the circular tube ; the 

 ovaries hang down in two 

 masses on each side of the 

 chymiferous tubes ; there is 

 no connection between the 

 two pouches, except near 

 their point of attachment, 

 where they unite again. 



Younger specimens, meas- 

 uring about one and a half 

 to two inches, and not hav- 

 ing more than sixteen to twenty-four chymiferous tubes, resemble Sto- 

 mobrachium ; they differ, however, in the small number of tentacles. 

 The marginal capsules are large, elliptical ; the granules placed far 

 apart, two in each (c, Fig. 138) ; the tentacles taper rapidly from the 

 base (t, Fig. 138), the walls are thin, the lasso cells scattered irregularly 



over the whole surface. At the base of the 

 large tentacles we find a very prominent pro- 

 jection (s, Fig. 138), in the shape of a small 

 tentacle opening into the circular tube: it is not 

 exactly a spur, as in Lafcea ; it develops only 

 after the rudimentary tentacles, being a button 

 scarcely to be recognized when the tentacle is 

 already quite well formed ; there are usually only rudimentary tenta- 



Fig. 137. Quarter of the disk of Fig. 136, seen from the actinal side. 



Fig. 138. A magnified portion of the circular canal, showing the position of the spur of the 

 tentacles, s, s, and of the marginal capsules, c, between the tentacles, t. 



