3 16 CHAS. W. HARGITT. 



upon it. In 1880 Romanes {Nature, June 24, also "Jellyfish, 

 Star fish, etc.," 1885), whose experiments on various medusae 

 are well known classics, took occasion to repeat certain of them 

 on Limnocodium, chiefly in relation to light, temperature, tactile 

 localization, and reactions to sea water. In most respects he 

 found the reactions of Limnocodium comparable in almost every 

 respect with those performed on marine species. His experi- 

 ments in transferring the specimens to sea water was to test their 

 tolerance to a medium and environment to which their supposed 

 ancestors must have long been familiar, are interestingly the very 

 opposite of those above described. He had previously proved 

 that marine species were unable to endure a transfer for more 

 than ten minutes to fresh water, seldom for more than five, and 

 then with evident signs of more or less severe injury. In the re- 

 verse tests with Limnocodium he found that no reaction was ap- 

 parent for about fifteen seconds, when a more or less sudden col- 

 lapse resulted, with tetanus-like spasms of increasing intensity 

 till all sensory reaction ceases, and after a short time death en- 

 sues. An exposure to sea water for even one minute may end 

 fatally, even if the creature be promptly returned to fresh water. 

 Similar results followed an immersion in dilute sea water though 

 with less promptness. In very reduced sea-water (y^), sponta- 

 neous activity may continue for some time, but with gradual de- 

 cline till but slight response is given to stimuli. 



In conclusion he states " It will be seen from this account that 

 the fresh-water medusa is even more intolerant of sea water than 

 are the marine species of fresh water. It would appear that a 

 much less profound physiological change would be required to 

 transmute a sea water jelly fish into a jelly fish adapted to inhabit 

 brine than would be required to enable it to inhabit fresh 

 water. Yet the latter is the direction in which the modification 

 has taken place, and taken place so completely that the sea water 

 is now more poisonous to the modified species than is fresh water 

 to the unmodified. There can be no doubt that the modification 

 was gradual — probably brought about by the ancestors of the 

 fresh-water medusa penetrating higher and higher through the 

 brackish waters of estuaries into the fresh waters of rivers, and 

 it would, I think, be hard to point to a more remarkable case of 



