Fig. 3.—The fresh-water jelly-fish (Limnocodium) enlarged four times linear measurement, as it is seen dropping through the water in a glass jar. PT, one of the four principal tentacles. MR, the margin of the disc. Ve, the delicate muscular frill or velum.
[Transcriber’s Note: The original image is 2¾ inches (7cm) high and 2¼ inches (5.5cm) wide.]
All the specimens were males, and the puzzle was to find out how it reproduced itself. After a few seasons had passed I determined to solve this problem. I made the guess that perhaps the jelly-fish were budded off from a fixed weed-like polyp growing in the depths of the tank—as is the case with many of the marine jelly-fishes. I remember that one leading member of the council, which still presides over the destinies of the Botanic Gardens, confided to me in a hushed whisper his belief that Providence created this new jelly-fish year by year in the tank in honour of the august patroness of the Botanic Society—Her Royal Highness the Duchess of Teck. I was obliged to make an end of this flattering theory when I discovered, after long searching with my assistant—attached to the rootlets of floating water weeds a minute three-branched polyp ([Fig. 4]), from which, as we subsequently were able to observe, the jelly-fish were pinched off as tiny spheres about one-sixteenth of an inch in diameter. No females of this jelly-fish were ever discovered. The polyps lived on from year to year, and budded off each season a swarm of pretty but futile male jelly-fish. They ripened and died on attaining a diameter somewhat less than that of a shilling. There were many most interesting points made out as to their structure, mode of feeding, and growth. You could keep them in a tall glass jar supported over a small gas-jet (they lived best at a temperature of 80° Fahr.), and they would swim up by a series of strokes to the top of the water, and then drop like little parachutes through the eighteen inches of depth to the bottom—taking in water-fleas and such food on the way—and immediately would start upwards again. I used to take them alive in my pocket corked up in a test-tube to show to friends.
Fig. 4.—Four of the minute club-shaped polyps adhering to a root-fibre of a water-plant. The rounded end becomes nipped off and swims away, free, as a young jelly-fish.
After they had disappeared from the tank in Regent’s Park (owing to some unhappy cleaning of the tank) they suddenly, in 1903, appeared—it seems incredible—at Sheffield! Then they briefly showed up in 1905 at Munich, and at Lyons had been captured in 1901—always in a tepid water-lily tank! We never could make out where they came from originally. Of course, the polyp must have been brought into the tank with some bundle of water plants from a tropical lake or river, but we never had any indication as to when or which.
Since the days of the fresh-water jelly-fish of Regent’s Park, which was called (a name, but why should it not have a name?) Limnocodium Sowerbii—a jelly-fish of about the same size ([Fig. 5]) but very different in shape and tentacles—was discovered in the great African fresh-water lake Tanganyika—in enormous numbers, and was named Limnocnida Tanganyikæ. Only five years ago the same jelly-fish was discovered in the Victoria Nyanza, and a little earlier in backwaters of the Niger. It is a curious and significant fact bearing upon the history of these three areas of fresh water connected with the three greatest African rivers—the Congo, the Nile, and the Niger—that the same little jelly-fish is found in all of them.