CTENOPHORA. 719 



lobes. The two subtentacular rows of plates are short, and at their oral 

 ends are situated the ' auricles,' which are processes of the body, either 

 long and mobile, or short, the base sometimes of great extent reaching to the 

 mouth. The aboral surface of the auricles is beset with fine ctenophoral 

 plates, the movements of which are independent of those of the plates of 

 the subtentacular rows. The central nervous system lies at the bottom of 

 a deep and narrow furrow : the nerves are prolonged between the plates of 

 each ctenophoral row. The mouth is wide, and there is an oral groove 

 extending to the bases of the body-lobes. The interradial vessels spring 

 from the funnel. The meridional vessels form loops on the body-lobes and 

 communicate with the paragastric canals. The tentacle basis, which is 

 of great length, lies close to the oral pole and there is no tentacle sheath. 

 A tentacle furrow extends right and left to the auricles in which are 

 lodged lateral tentacles. These are numerous and stretch to the right 

 and left in the tentacle furrows in which they are upheld by peculiar 

 bent ciliary plates or hooks, so that their ends only hang down freely. 

 Encharis alone possesses a simple chief tentacle. The sexual products 

 are formed either in the short vessels which extend on either side from 

 the main meridional vessels beneath each ctenophoral plate (Eucharis, 

 Bolina alata), or in the walls of the vessels between successive ctenophoral 

 plates. 



The Cestidae have a band-like body, immensely elongated in the 

 stomachal plane, and very short in the funnel plane. The subtentacular 

 ctenophoral rows are reduced to a few plates (4-6) at the aboral pole, 

 whilst the sub-ventral rows extend along the aboral margin of the body to 

 its two extremities. The ctenophoral plates are placed obliquely. The 

 interradial vessels originate from the funnel. The sub-tentacular meridional 

 vessels course along the centre of each surface of the body and at its ex- 

 tremities fall into the sub-ventral vessels which follow the aboral margins, 

 bend round the two extremities and unite with two vessels which follow the 

 oral margin and are branches derived from the oral ends of the paragastric 

 canals. An oral furrow extends right and left along the central line of the 

 oral margin of the body. The tentacle basis has a great lateral length and 

 is protected by a tentacle sheath. A tentacular furrow starts right and left 

 from the sheath and reaches to each end of the body. There is no chief 

 tentacle, but a number of lateral tentacles are lodged in the furrows in 

 which they are supported as in Lobatae, their free ends hanging down into 

 the water 1 . The sexual organs are developed in Cestus along the aboral 

 margin of the body in connection with the^ sub- ventral vessels ; in Vexillum 



1 R. Hertwig's account of the tentacular apparatus differs from Chun's. The latter traces all 

 the lateral tentacles to the tentacle basis. The former thinks that they are freed periodically from 

 the basis, but that they remain attached to a narrow band of epithelial cells and muscle fibres on the 

 wall of each tentacular furrow, which dies away before it reaches the tentacle basis. 



