Leptodora hyalina. 
351 
one, although careful search was made for them in both years. 
The number of the species is so irregular that the average per 
square meter represents very little. On August 22nd, 1895, the 
species was present in the upper meter at the rate of nearly 
2700 per cubic meter. These were all young females, either 
without eggs or having the eggs just laid. On October 6th, 
1894, three sets of observations gave respectively a catch of 9, 
38, and 13 individuals. On July 19th, six catches, at different 
hours, gave 0, 34, 11, 4, 3, 0. On August 1st and 2nd, there 
were taken: 4, 24, 16, 10, 4, and 2 individuals at different 
hours. These examples are sufficient to show that the figures 
for Leptodora are subject to a far greater variation than those 
of the other Crustacea. For this reason, and also because the 
size and habits of Leptodora are quite different from those of 
the other limnetic Crustacea, the species has not been included 
in the total number of Crustacea. The maximum catch was 79,. 
Aug. 7, ’95; 75, June 22, 96; about 5,000 per sq. m. 
Males of this species appear in October, the numbers decline 
rapidly during November, and no individuals were caught by 
the vertical net after November 26th in either year. Horizon¬ 
tal collections, however, show that they were present until 
after December first. The limits of this species, therefore, ex¬ 
tend from the middle of May to the first of December, and the 
maximum numbers occur in late summer and early fall. It is 
worthy of note that in no year does the maximum number coin¬ 
cide with the production of males. This is to be expected, 
as the large summer catches were due to the presence of num¬ 
bers of young or half grown Leptodora at the place where the 
net was hauled. It is therefore not surprising that these 
swarms should be irregular, and they would not be expected at 
the time when the adult females are producing the winter 
eggs. 
Many observations were made upon the food of Leptodora , 
and it was found that they eat chiefly Cyclops and Daphnia. 
The attempt of the animal seems to be to squeeze out and swal¬ 
low the interior of the prey. In a considerable number of in¬ 
stances the intestine or the ovary of Daphnia , nearly entire,, 
was seen in the stomach of Leptodora , and only occasionally 
