80 THE VITAL FUNCTIONS. 



phagus is visible at the centre of Fig. 249, where 

 its cavity has the form of a cross. The stomach 

 has a quadrangular shape, as in the ordinary me- 

 dusae ; and from each of its four corners there 

 proceed vessels, which are continuous with its cavity, 

 and are distributed by endless ramifications over 

 the substance of the cupola, extending even to the 

 fringed margin all round its circumference. The 

 mode of their distribution, and their numerous 

 communications by lateral vessels, forming a com- 

 plete vascular network, is seen in Fig. 251, which 

 represents, on a larger scale, a portion of the mar- 

 ginal part of the disk. The two large figures (24.9 

 and 2o2) also show the four lateral cavities (it, u. 

 Fig. 252), which are contiguous to the stomach, 

 but separated from it by membranous partitions : 

 these cavities have by some been supposed to per- 

 form an office in the system of the Medusa, cor- 

 responding to respirati(^i ; an opinion, however, 

 which is founded rather on analogy than on any 

 direct experimental evidence. The entrances into 

 these cavities are seen open at e, in Fig. 249, and 

 at E, E, in the section Fig. 252. A transverse sec- 

 tion of one of the arms is given in Fig. 253, showing 

 the form of the absorbent tube in the centre ; and 

 a similar section of the extremity of one of the 

 tentacula, is seen in Fig. 254, in which, besides the 

 central tube, the cavities of some of the smaller 

 branches (b, b), which are proceeding to join it, 

 are also visible. The pendent tentacula of the 

 Physalida formerly described,* are tubular, having 

 at their extremities, absorbing orifices, which may 



* Vol. i. p. 179. 



