
FOOD AND FEEDING 

they sit with the head toward the opening and the claws ready to grasp any 
smaller creature or dead animal matter. They should not be introduced 
into the aquarium with fishes but kept by themselves and when acclima- 
tized can be fed on small particles of meat or the flesh of mussels or oysters. 
Rotirera. The Trochelminths, of which the wheel-animalcules form 
one group, consist of Rotifera andGastrotricha, generally fresh water forms, 
and Dinophilea of salt and blackish waters. About 25 species of Rotifera 
occur abundantly in the United States in almost all bodies of freshwater. 
They are of small size inclosed in a cuticle to form a stiff shell. At the 
anterior end are cilia by which the animal 
swims and brings food to the mouth, and at 
the posterior end is a small separate joint, the 
foot, to which two bristle-like structures are 
attached. The internal organs comprise an 

alimentary canal, and nervous, reproductive 
and excretory systems and mucus glands. 
They have dorsal antennx back of the an- 

terior end of the head. Reproduction is by FIG. 74. Rotifera, 
5 1. Branchionus rubens. 
eggs which are developed under the carapace. a Raeules loigieres 
The genera most generally distributed in the 3- Diurella tigris. 
United States are Branchionus rubens, Diurella tigris, D. tenuior; D. webert, 
D. porcellus, Rattulus gracilis, R. longiseta, R. bicristatus, R. carinatus and 
R. rattus. Fig. 74. In the author’s vicinity Dr. Joseph Leidy also identi- 
fied Acyclus inquietus, Apsilus lentiformis, Limnias socialis and a very con- 
siderable number of less common forms. Some of the parasitic forms on 
fishes resemble the free-swimming larve of Annelids and Crustaceans. 
GasrrotricHa. This small group of minute freshwater Trochelminths 
have spindle-shaped bodies with two longitudinal bands of cilia or swim- 
ming hairs on the ventral surface and the mouth surrounded with a circlet 
of hooked hair-like appendages. Chetonotus maximus 1s the most common 
form. They are harmless to fishes and spawn. 
Cotitectinc Natura Foon. For the collection of the minute water 
fauna a mull net attached to a pole and a covered tin pail are usually em- 
ployed. During the breeding and rearing season of the goldfish almost 
any ditch, pool or pond contains them in greater or lesser quantity; but 
the keeping of a supply is difficult as they may soon die and rapidly decom- 
pose, making frequent excursions to the pond necessary. To avoid this, 
breeders prepare a breeding tank in a shaded locality and a collection of 
what might be called pure cultures for propagation are made with a pipette 
or lifting tube, which closed at the upper end may be placed in the water 
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