250 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



(8) has also observed a crimson ring-canal in specimens 

 taken at St. Andrews. 



Alder, (3) describes and figures the medusa of Cory- 

 morpha nana, Alder, (= Halatractus nanus, Allman 4), 

 which he bred from the hydroid. Hseckel (15) considers, 

 from Alder's description of this medusa and from the 

 description of Euphysa aurata by Forbes, that the 

 medusa of Corymorpha nana and E. aurata are identical 

 and gives in his "System der Medusen " Halatractus 

 nanus as the hydroid of the medusa Euphysa aurata. I 

 believe Alder is the only person who has ever taken 

 Corymorpha nana ; and Hseckel apparently has not met 

 with Euphysa aurata. The figure given by Alder of the 

 medusa of Corymorpha nana has not the specific charac- 

 ters of E. aurata. The umbrella of Corymorpha is about 

 as long as wide, and thin ; the umbrella cavity is conse- 

 quently very large. The umbrella of Euphysa is always 

 longer than broad, and laterally very thick ; also about one 

 third of the aboral end is formed of solid tissue ; the 

 umbrella-cavity is small compared with the external size 

 of the umbrella. The manubrium of Corymorpha is long 

 and extends beyond the velum, but the manubrium of 

 Euphysa is about two-thirds the length of the umbrella- 

 cavity and has never been seen to extend beyond the 

 velum. Euphysa aurata may be easily recognised by 

 the shape and great thickness of the umbrella. I think 

 that the medusae of Corymorpha nana and Euphysa 

 aurata do not belong to the same species, and that the 

 hydroid form, if one exists, of Euphysa has yet to be 

 discovered. 



Haeckel (15) describes and figures in his monograph 

 another species of Euphysa — E. mediterranea — which he 

 obtained at Yillafranca. The umbrella is longer than 

 wide (3 mm. long, 2 mm. wide), and thick. Three tenta- 



