126 LAFCEA DUMOSA. 



at the base of the tentacles the walls are thick, and the sensitive 

 swelling quite prominent, having a dark pigmenlrspot. The Medusa, 

 when it escapes from the reproductive calycle, has a vertical diameter 

 of about one twentieth to one sixteenth of an inch ; the Hydromedu- 

 sarium is from a quarter to an inch long. 



In the next stage observed (Fig. 194) we find the rudimentary ten- 

 tacles of the previous stage fully developed, and at the same time the 

 thread-like cirri of the adult Lafoea. This stage is important, connect- 

 ing as it does, without any doul)t, two Medusae 

 which had thus far been placed in different 

 genera. The digestive cavity and the ova- 

 ries are nearly in the same condition as that 

 observed in young Medusa?, where the spur 

 and the different kinds of marginal appen- 

 dages were as well developed as in the adult ; 

 we have as yet, however, in the present 

 stage (Fig. 194), no trace of the spur or of 

 the club-like appendages of the circular tube found in the adult. 

 These club-like appendages of Lafoea and of Ptychogena show that 

 the marginal capsules, the compound eyes, the cirri, and the different 

 rudimentary appendages, are only modified tentacles. 

 Buzzard's Bay, Naushon (A. Agassiz). 



Cat. No. 151, Naushon, 1861, A. Agassiz. Hydromedusarium. 

 Cat. No. 271, Naushon, 1861, A. Agassiz. Medusa. 

 Cat. No. 438, Naushon, 1864, A. Agassiz. Medusa. 



Lafoea cornuta Lamx. 



Laf(£a cornuta Lamx. Expos. Method. 1812. 



Newfoundland (Lamom^oux). 



Lafoea dumosa Sars. 



Lafoea dumosa Sars ; in Yidensk. Forh. 1862. 

 Campanularia dumosa JonxsT. Brit. Zooph. 1838. 



Massachusetts Bay (A. Agassiz). Medusa. 



Cat. No. 433, Sea-Coal Bay, N. S., Anticosti Expedition, 1861. Hy- 

 drarium. 



Fig. 194. Young Medusa still ftirther advanced than Fig. 193. 



