INTRODUCTION. O 



sought after in the air, in our method of Hving, &c., but 

 in the incautious use of waters, often abounding in innu- 

 merable animalcules."* 



According to Miiller and Straus, the greater number 

 of the Entomostraca, not parasitical, live upon vegetable 

 matter, and not upon animals ; and the former, in an 

 experiment he instituted, says,t that in keeping a 

 number of species, such as the Daphnia jpennata and 

 lon(/ispina, Cypris strigata and pilosa, Lynceus sjjJiericus 

 and Cyclops quadricornis, in the same water from 

 the 24th of July to the 22d of January, during which 

 time the water had evaporated from a depth of five 

 inches to that of one, he frequently subjected small 

 quantities of this water to the microscope, and was never 

 able to discover any animalcules in it upon the most 

 attentive examination, though the intestines of the Ento- 

 mostraca themselves were seen to be full, sufficiently 

 proving that they had not fasted during that time. This 

 assertion, however, I am much inclined to call in ques- 

 tion. The Cyprides particularly seem to be most vora- 

 ciously carnivorous ; and I have invariably found it 

 exceedingly difficult to keep for a length of time any 

 other Entomostraca alive in the same vessel with the 

 larger species of Cypris. In a vessel, in which I have kept 

 full-grown Chirocephali, there were mixed with them 

 many specimens of the Cypris tristriata. In a few days 

 the Chu'ocephali might be seen to become languid in their 

 movements, and assume an unhealthy appearance. The 

 Cyprides had become their deadly enemy. They might 

 be seen ever and anon to fasten themselves to the delicate 

 feet of the poor Chirocephali, and wofully impede their 

 course through the water ; and when, either from these 

 annoyances, or from any other cause, they ceased to be 

 able to move with any degree of rapidity, hosts of these 

 little Carnivora might be observed to attack them before 

 life was extinct, anticipating as it were their victim's death. 



* Entomost., p. 12. -f Loc. cit., p. 7. 



