1908.] ON GONADIAL GROOVES IX A MEDUSA. 55 



2. On the Presence o£ Gonadial Grooves in a Medusa, Aurelia 

 aurita*. By T. GooDEY, i Student Demonstrator in 

 Zoology, University of Birmingham. 



[Received December 23, 1907.] 

 (Plate I.t) 



While recently examining specimens of the Sc}'phozoon 

 Aurelia aurita in the ordinary course of practical woi-k in the 

 Zoological Laboratory, the structures mentioned in the title of 

 this paper attracted my attention. It was not clear that they 

 formed any part of the ordinary radial canal-system, and, so far, I 

 have been unable to find any account of them in the different 

 text-books and journals which I have consulted in the expectation 

 of obtaining information as to their nature. This being the case, 

 it seemed desu-able to investigate the nattu^e and relations of the 

 structures in question and to give a brief account of the i-esults. 



The gonadial grooves were found in all the preserved specimens 

 examined in the laboiutory, both male and female, and they were 

 also found in living examples which came under my notice during 

 the recent summer vacation. 



In a view of the sub-umbrella surface (PI. I. fig. 1) the four 

 grooves were easily visible to the naked eye, and presented the 

 appearance of four radially arranged canals. Each groove (g.g.) 

 lies in an inter-radial axis, and is better seen when the prolonged 

 mouth-angles have been removed. It has al^out the same dia- 

 meter as the origin of an ordinary per-radial or ad-radial canal, and 

 extends from the central gastric cavity into a gastric pouch (g.p.), 

 where it terminates in a somewhat funnel-like expansion at about 

 the centre of the pouch and directly dorsad to the external opening 

 of the corresponding sub-genital pit (s.p.). In its course the 

 groove extends along the ventral wall or floor of the passage from 

 the gastric cavity to the pouch and along the floor of the pouch 

 itself. 



Bristles could readily be passed along the groove, and by means 

 of a fine pipette a coloured liquid was injected through the 

 groove into the gastric pouch. When the latter became filled 

 and more of the liquid was injected, the excess began to flow back 

 into the gastric cavity through the main opening into the pouch 

 (PI. I. fig. 2, d.e.p.) which is dor.sad to, and considerably wider than, 

 the groove in question. 



At fii^st sight the grooves appeared to be the beginnings of 

 inter-radial canals ; but the fact that each groove does not extend 

 beyond the centre of each gastric pouch, and also that at this 

 point it widens out and abruptly terminates, negatives this idea. 



In order to determine the true nature of these structures, 

 portions of the Medusa, including complete gastric pouches and 



* Communicated by Professor Bridge, F.R.S., P.Z.S. 

 tt For explanation of the Plate, see p. 58. 



