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 



