198 COELENTERATA. 



in different planes. The long diameter of the stomach lies in one 

 of the two planes mentioned above, while that of the funnel lies 

 in the other plane, which is at right angles to the first. These 

 two planes are called the stomach-plane* (Fig. 158, M t M.) and 

 funnel-plane (T, T.) respectively. 



The stomach-plane divides the body into a right and left half; 

 but it is impossible to speak of the two parts of the body marked off 

 by the funnel-plane as dorsal and ventral, or as anterior and posterior, 

 as is done by some authors, because these two parts are identical and 



FIG. 158. Diagram of a Cydippe seen from the aboral pole (after Chun). M-M stomach 

 (sagittal) plane ; T-T funnel (transverse) plane ; ri to r the eight rows of vibratile plates ; 

 p polar plates ; n^ to % the eight ciliated grooves ; t.b base of tentacle ; t.st stalk of tentacle ; 

 tt branch of tentacle ; scJi sheath of tentacle ; sch.o opening of tentacle-sheath ; c.pr per- 

 raclial vessel; c.ir interradial vessel; c.adr adradial vessel ; sp 1 to sp 8 the sperm producing, 

 oiA to ov8 the ova-producing sides of the eight meridional vessels ; t.g tentacle vessel ; 

 ex 1 and ea; 2 the two aboral openings of the gastrovascular system. 



not distinguishable from one another by any differential character. 

 The tentacles when present are two in number : they arise from the 

 sides of the body in the funnel-plane (Fig. 158, T, T). Further, we 

 may speak of two transverse axes a stomachal axis passing through 

 the long diameter of the stomach, and a funnel axis passing through 

 the long diameter of the funnel. 



The body (Fig. 157) carries eight meridional rows of vibratile 



* The plane of the stomach is sometimes called the sagittal plane, and that of 

 the funnel the transverse plane. 



