INTRODUCTION. 
5 
sought after in the air, in our method of living, &c., but 
in the incautious use of waters, often abounding in innu- 
merable animalcules.”* 
According to Muller 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 Baphnia pennata and 
longispina , Cypris strigcita and pilosa , Lynceus sphericus 
and Cyclops quadricornis , in the same water from 
the 24th of July to the 2 2d 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 Chirocephali 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. 
