THE FRESH-WATER MEDUSAE OF BOSS LAKE, ELKHART, 
INDIANA. 
Abstract. 
i’. PAYNE. 
September twenty-second, 1919, I was informed that medusae were abun- 
dant in a small artificial lake near Elkhart, Indiana. Five days later I 
visited the place and verified the statement. In fact they were so abundant 
that one could bring in a hundred with a few sweeps of the net. A second 
visit was made two weeks later but not a single specimen could be found. 
The weather had become much colder, to the point of freezing, and no doubt 
the change in the temperature caused their death. A few days later Mr. 
Boss informed me that the surface of the lake was strewn with fragments 
of medusae. All specimens examined were females. A few specimens 
were found the previous summer. 
During the summer of 1920 the lake was watched carefully from June 
twenty-first until October second. The hydroid was found June twenty- 
eighth on material collected June twenty-first. These hydroids were ob- 
served to form sausage shaped buds which separated from the parent and 
formed new hydroids. Other buds remained attached, thus forming col- 
onies. The largest colony found had seven hydroids. <A third type of bud 
formed the medusa. 
The first medusa in the summer of 1920 was taken July sixteenth. It 
was about one-half inch in diameter. The rest of the summer they were 
abundant, but not so numerous as they were on my first visit of the previ- 
ous year. Again all the medusae were females. This, along with the fact 
that on previous discoveries of this medusa all the specimens were males, 
has puzzled me somewhat. The females became sexually mature and shed 
their eggs but they did not develop so far as my observations went. Plank- 
ton catches at all seasons and depths have shown no free swimming larvae. 
Neither has a close examination of the weeds, sticks, stones. and surfaces 
of boards and posts shown anything of the sort. But why is there only one 
sex? I do not know but the facts lead me to wonder whether the hydroids 
may not be male and female producing. 
How the forms got into the lake is doubtful. The hydroids are very small 
and might occasionally become attached to fishes and thus be transferred. 
Neither do I see any reason why they might not be carried by wading birds. 
The hydroids live over the winter in the form of contracted masses. 
