December 15, 1916] 



SCIENCE 



859 



object, a few inches below the surface, looking 

 so much like a bit of rubbish that it would 

 certainly not have been recognized had we not 

 been looking for it. Then several were seen 

 near each other, then a few scattered individ- 

 uals, which were all carefully taken into 

 bottles, or with a small collecting net. Finally 

 in the center of the stream we encountered 

 them in numbers and from that time until it 

 began to get too dark to see well, the boat was 

 generally surrounded by them. There were 

 four people in the boat filling bottles and jars 

 rapidly and in a few minutes we gathered 

 some scores. Often with a single movement of 

 the net I captured several and before taking 

 it in had secured a half dozen or more. 

 Dozens were in sight at one time, and it was 

 soon evident that Mr. Bridgemord was right, 

 and that in truth there were millions of these 

 medusae in the stream. I have worked on the 

 aquatic animals of Kentucky waters for many 

 years and was not prepared to believe that 

 medusae would ever be found within the state 

 in such numbers, nor indeed in any fresh 

 water of the United States. Several hundred 

 living individuals were brought back to 

 Lexington with me, and some of them were 

 alive until the afternoon of September 28. 

 One by one they died in our city water, though 

 it was kept running slowly through the 

 aquarium in which they were confined. The 

 temperature may have been too low or the 

 water otherwise unsuited to them. A good 

 many were fixed with corrosive sublimate and 

 preserved, so it may be possible to study them 

 fully and determine something of their rela- 

 tionships. 



Like others of their kind they are hyalin, ex- 

 cepting the flap-like yellow reproductive bodies 

 attached to the four radial canals close to the 

 stomach. The umbrella-shaped body is widely 

 convex, the depth (in life) being perhaps one 

 third the diameter. It measures from about 

 14 to 15 millimeters across. The manubrium 

 is prismatic and extends downward to the 

 level of the outer margin of the umbrella; the 

 mouth is surrounded by an eight-lobed rosette. 

 At the margin of the umbrella are four long 

 tentacles (perradial), measuring about 14 

 millimeters, which are attached a short dis- 



tance above the margin, and in life are dis- 

 posed to extend upward. Secondary more 

 slender tentacles are about half the length of 

 these large ones and are also attached above 

 the margin; then still nearer the margin are 

 numerous minute tentacles thickly crowded 

 at their bases. 



Where this multitude of medusas came from 

 is a mystery. Mr. Bridgemord, who first saw 

 them, has fished in the stream for a good 

 many years, but never saw one until Septem- 

 ber 26. I myself have several times examined 

 the upper part of the creek rather carefully 

 in search of Simulium larvae, and while Polyzoa 

 (a Plumatella) were abundant on the rocks, 

 nothing resembling a hydroid was present in 

 the water. My examinations were made some 

 years ago, however. The hydroid generation 

 in the stream ought to be easily discovered if 

 the myriads of medusae are any indication as to 

 its abundance. I have not yet had an oppor- 

 tunity to search for this stage, but expect to 

 do so at once. 



Of the three genera to which fresh-water 

 medusae have been assigned, the Kentucky 

 species belongs unquestionably to Craspeda- 

 custa. Dr. Mayer 1 describes C. sowerbyi, first 

 discovered in a lily tank in Regent's Park, 

 London, and later found in other parts of the 

 world, as 12 millimeters wide. The Kentucky 

 examples are somewhat wider, but in other 

 respects agree closely with Dr. Mayer's de- 

 scription, excepting in the length of the manu- 

 brium, which he says extends half its length 

 beyond the velar opening, whereas in Ken- 

 tucky examples it reaches to about the level 

 of the bell margin. In this respect the latter 

 agree with the 0. kawaii, described by Oka 2 

 from the Yang-tse-kiang River, China, but 

 differ again and agree with 0. sowerbyi in 

 having but three ranks of marginal tentacles 

 instead of seven. Dr. Mayer 2 thinks the Chi- 

 nese species may be an exceptionally flourish- 

 ing form of 0. sowerbyi. The Kentucky ex- 

 amples are still nearer the medusae described 

 from Regent's Park. Thaumantias lacustris 

 from a fresh-water lagoon in Trinidad is very 



i "Medusa; of the World," 1910. 



2 ' ' Annotationes Zoologies, ' ' Vol. 6, 1907. 



3 Loe. cit. 



