1884.] Limnocodium Sowerbii, Alhnan and Lankester, 



13 



March. 10, 1882. Tank filled at Regent's Park. 



No Medusae observed anywhere during this year (1882). 

 March 8, 1883. Tank filled at Regent's Park! 

 April 28, 1883. Medusae appeared at Regent's Park, adult and 

 young. 



July 13, 1883. Nipping off of spheres from the genital sacs first 

 noticed. 



July 14, 1883. Ten adult Medusae in clean water transferred to 

 Kew. These were never seen again. 



July 25, 1883. All Medusae disappeared. The tank at Regent's 

 Park was not emptied during this winter. 



April 27, 1884. Two specimens of adult Medusae observed at 

 Regent's Park. 



May 28, 1884. Adult and young Medusae next observed, and in 



great numbers. 

 June 20, 1884. Very few Medusae observed. 

 June 30, 1884. Medusae almost had disappeared. 

 Nov. 28, 1884. Hydriform organism seen on Pontederia roots 



when tank at Regent's Park was emptied. 

 Nov. 30, 1884. Pontederia root bearing hydroid placed in Kew 



tank. 



Dec. 1, 1884. Tank refilled at Regent's Park. 



General Remarks. 



That this new and in many ways most remarkable hydroid, appear- 

 ing in fresh water in great quantities, in the tank where Limnocodium 

 appeared, and upon the roots of a plant which was introduced just 

 before Limnocodium appeared, is a phase in the life-cycle of Limno- 

 codium seems so highly probable, that we may take it for granted at 

 present. Incontestable proof will, I hope, be furnished next spring 

 by tracing its further development. 



As it seems extremely probable that during next summer we may 

 be able to explain fully the life-cycle of this most interesting orga- 

 nism, it is not necessary to devote much time now to speculating upon 

 what that cycle will probably be. 



The connexion of the organism with Pontederia, first suggested by 

 Professor Lankester, seems to be borne out by the fact that only upon 

 the Pontederia roots can we find the hydroid form. That the Limno- 

 codium did not establish itself at Kew may be owing to the fact that 

 there was no Pontederia in that tank. 



In dealing with the hydroid form here described, we must remember 

 that Limnocodium is undoubtedly one of the Trachomedusae. No 

 trachyline form has before this been shown to be connected with any 

 hydroid condition, but we know less about the Trachomedusa? than 



