82 MOLLUSCA, CRUSTACEA AND EEPTILIA FOR 



In fresh water are also found two more little creatures 

 allied to the shrimp ; one, the Branchipus stagnalis, is found, 

 as its name indicates, in stagnant pools, and the other, 

 Cyclops quadricornis, is found also in similar water and 

 is excellent food for fish. Many others of these miscrosoo- 

 pic animals, some of them crustaccous, are found in fresh 

 water and may be introduced for the purpose of studying 

 their habits. 



The reptiles come next in our list, and we shall begin 

 with the consideration of the frog, whose young, the tad- 

 poles, are such useful servants iu our Aquarium. 



The Bull-frog (liana pipims) is the common frog of our 

 ponds, and it is the tadpole of this species that we see 

 in such large quantities in ponds and brooks. Dr. De 

 Kay speaks of it as follows: "The Bull-frog is one of 

 the largest of the family in this State, and appears to be. 

 generally distributed throughout the Union. It is well- 

 known by its hoarse voice, compared by many to the 

 roaring of a bull, and which is so loud as to be heard at 

 a great distance ; it is aquatic, although it occasion- 

 ally comes to land. In the adult state it feeds on 

 insects, crawfish, helices and small fish. The tadpole 

 (PI. V., Fig. 6), on the other hand, appears to be exclu- 

 sively herbivorous." The changes that the Bull-frog under- 

 goes in its transition from the egg to the perfect ani- 

 mal, arc curious and will well repay a careful examina- 

 tion ; but it is generally in the tadpole state that we 

 procure our amphibia, and from that state to the one of 

 the frog we can observe the transitions. The tadpole 

 has gills, or rather only one, on one side of his head, 



