260 Miscellaneous. 



numbers : larvoc of frogs and insects, species of Daphnids, Naids, 

 Chcetogaster, Dero, ^olosoma, Clepsine, Planorhis, Physa, and Ancy- 

 lus were so richly represented in individuals that the spectator 

 might easily declare the water to be fresh without even testing it. 

 The touguo was in fact the only test applied ; but it was universally 

 agreed that no saltness was perceptible to the taste. Our horses, 

 too, drank the water unhesitatingly, without being especially 

 thirsty, and horses are there considered to be particularly discrimi- 

 nating in the matter of water. On these grounds I believed that I 

 was entitled to claim my jellyfish as a freshwater animal, and am 

 still of this opinion, the more so since several examples of Medusae 

 have already been discovered in freah water — Lhniiocodium in the 

 Vktorla-rerjia ponds in Kew Gardens and a Medusa from the Tan- 

 ganyika Nyanza. 



If I now attempt to describe the freshwater Medusa from Trini- 

 dad, and to assign it to its proper systematic position, this is unfor- 

 tunately only possible for the sexual form, the free-swimming jelly- 

 fish, since I did not succeed in discovering a hydroid at the same 

 spot from which it might have sprung. Apart from the possibility 

 that I did not make a sufficiently exhaustive search, it would alst) 

 be conceivable that the hydroid generation had died down at that 

 season of the year (March), a not impossible event in the case of 

 a tender organism proceeding from the sea, considering the high 

 temperature of the water at that period and that at another season 

 of the year the hydroid form would aj^pcar again ; or we may sup- 

 pose that the hydroids live in the sea, and that their Medusae alone 

 pass into the lagoon at the rainy season, when there is a communi- 

 cation with the ocean, and adapt tliemselves, at least partially, to a 

 freshwater existence. It must be confessed that the probability of 

 the latter theory is but small ; for in none of the Medusae which I 

 collected were the sexual products perfectly ripe, so that we may 

 assume that they had not very long separated from their place of 

 origin. Communication between the water in which they were 

 living and the sea had at that time been severed for at least two 

 months. If they had been cut off from the sea as Medusae this 

 interval would well have sufficed for the attainment of full sexual 

 maturity. 



It is, however, alwaj's a serious matter to assign a species to its 

 place in a system on the basis of one developmental stage only, 

 when that system is to a large extent constructed on the morpho- 

 logical and structural relationships of the asexual generation and on 

 the mode of development of the sexual form. Nevertheless it 

 appears desirable so to characterize the animal that later investi- 

 gators who may happen to take up the study may be able to recog- 

 nize it and determine its position and affinities to better purpose. 



The diameter of the bell of the little craspedote Medusa is from 

 2 to 2h millim., and in shape it is strongly arched, so that even 

 when expanded to its utmost extent it is still almost hemisiiherical, 

 and considerably more than hemispherical when in a state of con- 

 traction. The muscular ring at the margin of the bell is powerfully 

 developed and is capable of contracting so strongly that the aper- 

 ture of the velum b«^omes almost closed. The velum itself is thin 



