730 Proceedings of the Royal Irish Acade)ny. 



Haeckel, in his "System der Medusen," has altered Gosse's 

 description in the following manner : — Sixteen large club- 

 shaped tentacles, in eight groups of tioo each. Between them 

 twenty-four sense-organs (eight adradial groups of three each) 

 and eight short and delicate spiral tentacles. It will be seen 

 that Haeckel has removed the smallest tentacle fi'om each group 

 and placed it alone by itself. Gosse clearly states that the three 

 tentacles are close together, and his excellent illustrations fully 

 bear out his description. 



The examination of the Valencia specimens throws light upon 

 the subject, and shows that the position of the tentacles is 

 regulated by the order of their development. 



Gossea circinata is distinguished from G. corynetes by Haeckel 

 by possessing eight groups of three tentacles in each, and short 

 spiral tentacles, one about midway between every two groups. 

 If Haeckel had kept strictly to Gosse's description of G. cory- 

 netes, then both species would have been alike in the number 

 of tentacles in each group, and the difference would have been 

 in the additional eight single solitary tentacles found in 

 G. circinata. 



The following is an abstract of Haeckel' s description of Gossea 

 circinata : — Umbrella semicircular, a little broader than high. 

 Stomach one-third as long as the length of the umbrella ; mouth 

 with four crenated lips. Gonads club-shaped swellings occu- 

 pying about two-thirds of the radial canals, and leaving both 

 ends free. Twenty -four large club-shaped tentacles, in eight 

 groups of thi'ee each ; between them twenty -four marginal 

 sense-organs (eight adi'adial groups of thi'eeeach). Eight short 

 and small spiral tentacles. 



Some of the Yalencia specimens agree fairly well witji 

 Haeckel' s description, but others show that more short tentacles 

 are developed upon the margin of the umbrella. None, how- 

 ever, correspond to the specimens taken by Gosse ; and for this 

 reason I have kept the two species apart for the present, though 

 I am strongly of opinion that Gosse's specimens are a stage 

 younger than those described by Haeckel. Some of the Yalencia 

 specimens are a stage older than Haeckel' s specimens. If the 

 size of a tentacle is regulated by its age, then the order of the 

 growth of the tentacles can be demonstrated. In each group the 

 tentacles are of different sizes — large, medium, and small ; the 

 same order existing in all the groups. The eight large tentacles 



