L.M.B.C. MEDUSA. 269 



was taken, about 4 mm. in diameter, with eight tentacles 

 in each group. Black ocellus at the base of each tentacle. 

 The oral tentacles have eight terminal branches, each 

 tentacle being three times dichotomously divided. 



These specimens illustrate very well the increase in 

 number both of the marginal tentacles and of the branches 

 of the oral tentacles. The young medusa usually leaves 

 the hydroid with two tentacles in each group, and the 

 oral tentacles are either simple (unbranched) or with a 

 single branch. 



On April 28th I captured two specimens, which are 

 certainly an early stage of a Margelis. The umbrella 

 about f mm. in diameter. The umbrella cavity is almost 

 obliterated by the thickness of the umbrella. Three 

 marginal tentacles, unequal in size, in each of the four 

 groups. One specimen has one oral tentacle unbranched, 

 and the other three with one branch. I think these are 

 probably the young stages of Margelis ramosa, with an 

 abnormal growth of the umbrella. 



The medusa Bougainvillea britannica, Forbes, is the 

 adult stage of the medusa which is liberated from the 

 hydroid Bougainvillia ramosa, Van Beneden. Wright 

 (22) in 1857 succeeded in rearing medusae from the hydroid 

 colonies of Atractylis ramosa ( = Bougainvillea ramosa, 

 Van Beneden). The young medusae first had four simple 

 oral tentacles, and eight marginal tentacles, two in each 

 group. Stomach and tentacle-bulbs of an orange colour. 

 A black ocellus at the base of each tentacle. Wright was 

 able to keep his specimens alive and saw further develop- 

 ment. The oral tentacles became first once, and after- 

 wards, twice dichotomously divided. Additional tentacles 

 also developed in the marginal groups. The greatest 

 number observed was six, and each one had a black ocellus 

 aJ; its base. At the same time the generative products 



