58 ON GONADIAL GROOVES IN A MEDUSA, [Feb. 4, 



According to the discoverer, the two pairs of gonads apparently 

 had their origin from endodermal cell proliferations of the walls 

 of genital diverticula of the general archenteric canal-system, as in 

 so many other Ccelenterata. Special genital ducts are present, but 

 variable in number, and they are described as being continuous 

 with the tunica pi-opria investing the gonads. The external 

 apertures of the ducts ai-e situated on the dorso-lateral surfaces 

 of the body, below several of the ctenophoral bands. 



In the present state of our knowledge of the genital ducts of 

 Ctenoplcma korotneffii, and especially in the absence of any 

 information as to their mode of origin, any attempt to discuss the 

 question of their morphological character would be of little value. 

 It may therefore be concluded, at any rate provisionally, that, 

 while both Aiirelia and Ctenojjlana stand alone among living 

 Ccelenterata in possessing genital ducts, it is nevertheless only in 

 the Scyphozoon that these structures can at present be regarded 

 as coelomic or archenteric derivations, and, in fact, are a very 

 primitive form of coelomoduct or gonoduct. 



I am indebterl to Professor Bridge for the kindness and 

 consideration which he has shown to me in these my first attempts 

 at independent investigation, and also to Mr. F. W. Crispe for the 

 material help given in the preparation of the sections. 



EXPLANATION OF PLATE I. 



Gonadial grooves in Aurelia aurita. 



FJo-. 1. Surface view of sub-umbrella aspect of Aurelia aurita, the prolonged mouth- 

 angles having been removed. The gonadial grooves are shown, and also 

 their relations to the surrounding structures. 



Fig. 2. Semi-diagrammatic, enlarged three times. The gastric pouch has been cut 

 through along the inter-radius, and the drawing represents a view taken 

 in the vertical plane. The space between the dotted line and the body- 

 wall represents the course of a gonadial groove from the gastric cavty to 

 its opening into the gastric pouch. 



Fig. 3. (X 20) Section passing through the main passage to a gastric pouch,^ 

 showing the gonadial groove lying in a median position in the ventral wall, 

 bounded on either side by an endodermal epithelial fold. 



Fig. 4. (X 20) Section passing through a gastric pouch, showing a gonadial groove 

 in the iloor, and the loops of the gonad ring bounding it on every side. 



Refeeence Letters. 

 h.w., body-wall ; d.e.p., dorsal entrance to a gastric pouch ; e. (fig. 3), epithelial 

 fold's ; e, el, e^, e^, epithelium lining inside of pouch and covering gonad above ; e-*, 

 €<>, epithelium of ventral surface of the gonad and of the floor of a gastric pouch ; 

 g'., gonad ; g.g., gonadial groove ; g.j>., gastric pouch ; m.f., main passage from the 

 gastric cavity to a gastric pouch ; s.p., sub-genital pit. 



[J/arcA ^th, 1908. — Since writing this paper my attention has 

 been directed by Mr. E. T. BroAvne of University College, London, 

 to a paper published by L. Agassiz in ' Contributions to the 

 Natural History of the United States,' vols. iii. & iv. 1860-62, 

 dealing with Aurelia Jfavidula, which is now considered to be the 

 same as Aurelia aurita. 



In his account L. Agassiz explains that the gastric pouches 



