198 



HOMOLOGIES. 



rcnion (/),wliicli corresponds to the manubrium with that portion of the umbrella which, with its 

 associated structures, is projected round the manubrium in the form of a bell. 



Now, in ?kBeroe (woodcuts, figs. 73 and 74) the manubrial region is never developed, and the 

 body is represented by the atrial region alone. From the atrium (3', b') contained within this 

 ret^ion two radiating canals {a, a) are given off. These immediately divide and subdivide so as to 

 become ultimately eight, which are, moreover, united at their distal extremities by a circular 

 canal, which corresponds to that of the medusa, though here thrown back by the non-development 

 of the manubrial region of the umbrella. Besides the eight longitudinal canals (.?•, x) into which 

 the two radiating canals ultimately subdivide, these two canals give off, each immediately after its 

 orio-in, an accessory canal [x, x) which runs without division close to the main body-cavity 

 towards the oral orifice, and opens like the others into the circular canal. 



The generative sacs {d, d') are developed as diverticula along the course of the radiating 

 canals, whence they extend into the gelatinous substance of the body. 



Fig. 73. 



Fig. 74. 



Diagramatic longitudinal section of 

 Beroe in a plane at right angles to 

 that of the compressed somatic cavity. 

 In order to give a sufficiently com- 

 prehensive view of the structure, a 

 few parts are here represented which 

 are in reality somewhat removed from 

 the plane of the section. 

 a, a. Transverse portion of the radiat- 

 ing canal system, two of the primary 

 tranches being shown as if cut off close 

 to their origin ; x, x, meridional portion 

 of this system ; x\ x\ deep or accessory 

 canals, their distal terminations in the 

 circular canal cut off ; c, lumen of cir- 

 cular canal ; 6', h' , somatic cavity ; t, one 

 of the aboral outlets of the somatic 

 cavity ; *, valve-like processes of the 

 inner surface of the somatic cavity; 

 d, d', generative sacs, male and female. 



Diagramatic transverse section of 

 Beroe. 



b' Somatic cavity; x, x, meridional 

 portion of the radiating canal system ; 

 x' x', deep or accessory canals; d, d\ 

 generative sacs, male and female; y, 

 vibratile lamella;. 



Leuckart^ insisted on the association of the Ctenophora with the Actinozoa rather than 

 with the Hydrozoa, and the same view of their affinities has been advocated by Huxley. 

 According to this conception of ctenophoral homologies, the ctenophora must be provided with a 

 stomach-sac differentiated, as in the actinozoon, from the general body-cavity. Now, though the 



^ Frey und Leuckart, * Beitriige/ p. 35. 



Huxley, " Lectures," in ' Med. Times.* 



