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. 



RoTiFERA. The Trochelminths, of which the wheel-animalcules form 

 one group, consist oi Rotifer a zxidiGastrotricha, 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 antennae back of the an- 

 terior end of the head. Reproduction is by fig. 74. Rotifera. 

 eggs which are developed under the carapace. ^. ;j^„„/„ /„„^,v^«. 

 The genera most generally distributed in the 3- Diureiia tigris. 

 United States are Branchionus rubens, Diureiia tigris, D. tenuior; D. weberi, 

 D. porce/Ius, Rattulus gracilis, R. longiseia, 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 larvae of Annelids and Crustaceans. 



Gastrotricha. 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. Chatonotus maximus is the most common 

 form. They are harmless to fishes and spawn. 



Collecting Natural Food. 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 prbpagation are made with a pipette 

 or lifting tube, which closed at the upper end may be placed in the water 



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