1032 The American Naturalist. [December, 
cell to another, being, like Gromri’s pseudopodia, unstable 
sensitive, conductive, contractile, we are on the road to admit not 
only the existence of such statical ectosarcal connections as 
Hammar discovers, but to accept as working hypothesis a 
conception of these bridges as dynamical factors of the greatest 
importance. 
A NORTH AMERICAN FRESH WATER JELLY FISH. . 
By Epwarp Ports, 
On June 10, 1880, the first known fresh water jelly fish 
(Limnocodium sowerbii, Allman & Lankester) was discovered in 
the Victoria Regia tanks in Regent’s Park, London. Near the 
end of November, 1884, a primitive “hydriform organism ” 
from which it was supposed the jelly fish might have been de- 
rived, was found in the same tanks and described by Alfred 
Gibbs Bourne.’ 
About two months after Mr. Bourne’s discovery, I first de- 
tected Microhydra ryderi upon some stones collected the pre- 
vious autumn from the rocky bed of Tacony Creek, a rapidly 
flowing mill stream near Philadelphia, Pennsylvania, a small 
affluent of the river Delaware, but far above tide level. Some 
peculiarities in its structure and mode of gemmiparous multi- 
plication were described by my valued friend the late Dr. John 
A. Ryder.’ 
Dr. Ryder had not, at the time of writing the above paper, 
seen the living organism which he there described. Speci- 
mens were, however, some years later, placed in his hands for 
study and watched for many months with exceeding interest. 
His early death has left in the possession of his representatives 
many excellent drawings and some valuable micro-slides as 
the only evidences of his interest and labor. No descriptive 
‘The Living Substance. G. F. Andrews. Boston: Ginn & Co., 1897. 
* Proceedings of the Royal Society, Dec. 11, 1884, Vol. 38, p. 9, ete. See also 
_ paper by F. A. Parson, Jour. of Queckett Club, 2nd series, vol. 2, 1885-6. 
~ _ "American Naturalist, Extr , Dec., 1886, p. 1232, ete. 
