ACTINOZOA. 227 



it merges into the cylindrical part of the tentacle." 

 Professor Agassiz describes the latter not as hollow 

 but solid, though he recognizes the two layers of 

 which it is composed. 



In Callianira two long tentacles, relatively 

 situate as in Pleurobrachia, but destitute of 

 lateral threads, divide, at their free extremities, 

 into two or three lengthened branches {Jig. 39, d). 



In CestuTTi, also, a pair of symmetrical tentacles 

 appear to be usually present, but these do not, as 

 in the preceding forms, issue from the equatorial 

 region, thence turning away from the mouth ; but, 

 rather, take their position in front of and behind 

 the latter, towards which they are seen to incline. 

 Milne Edwards figures the tentacles of C. Veneris 

 as simple ; by other writers, and perhaps in other 

 species, they are described as variously branched. 



Among the lobed Ctenojphora the particular 

 homologies of the tentacular apparatus have 

 hitherto been by no means sufficiently studied. 

 In Chiajea occur two tentacles, one on each side 

 of the body, but similar in other respects to those 

 of Cestum. Tentacles of the second type are, 

 however, more frequently to be met with in this 

 section of the order, and these may be either 

 lateral, and arranged in groups, as in most genera, 

 or disposed in a ring round the mouth, as in 

 Eurhcmiphoea. 



In Bolina a tuft or brush of very short tentacles 

 is seen to arise on either side of the mouth, where 

 the oral vessels appear to meet, about midway in 

 their course, the superficial paragastric canals. 

 The extremity of each of these canals ends in a 

 simple socket, within which the tuft of tentacles 

 may be withdrawn. But there is no proper sac, 



Q 2 



