230 TROCHELMINTHES 



FAMILY 2. GIGANTOKHYNCHIDAE. 



Body large, and annulated; lemnisci long and twisted: 1 genus. 

 GIGANTORHYNCHUS Hamann. With the characters of the family: 

 1 species. 



G. hirudinaceus (Pallas) (G. gigas Block) -(Fig. 

 367). Body white, tapering posteriorly, proboscis almost 

 spherical and with 6 rows of 8 hooks each; male 6 to 9 

 cm. long and 4 mm. thick; female up to 50 cm. long and 



Fig. 367 4 to 9 mm. thick : in the intestine of pigs and often a 



Gigantorhynchus . . 



giga* (Ward). common and dangerous parasite; the intermediate host a 



B, male. beetle grub, which pigs often eat. 



SUBPHYLUM 3. TROCHELMINTHES. 



Minute, aquatic animals which in structure bear a close relation to 

 the trochophore larva of the annelid worms and mollusks. The body is 

 unsegmented and often externally annulated or ringed and is never com- 

 pletely ciliated, although in most of them groups of cilia occur in certain 

 regions. A spacious body cavity is present, which is not however limited 

 by a peritoneum. The Rotifera, by far the largest of the three classes, are 

 characterized by the ciliated disc-like front end of the body and usually 

 also the forked organ of attachment at the hinder end. The other two 

 classes comprise a few species of peculiar microscopic worms which are 

 often included among the Rotifera, but which lack the anterior disc and 

 differ from them also in other important respects. The subphylum con- 

 tains 3 classes. 



Key to the classes of TrochelmintJies: 



Oi External cilia present. 



\ Anterior ciliated disc present 1. ROTIFEBA 



ft 2 Ventral surface only ciliated 2. GASTROTRICHA 



a s External cilia absent 3. KINORHYNCHA 



CLASS 1. ROTIPERA * 



Rotifers or wheel animalcules (Fig. 379). Microscopic, aquatic ani- 

 mals, the body of which is composed of three divisions, the head, the trunk, 

 and the foot. The head bears the corona, which is a ciliated disc forming 



* See "The Rotifera or Wheel Animalcules," by C. T. Hudson and P. H. Gosse, 

 1889. "The Rotifera of Sandusky Bay," by D. S. Kellicott, Proc. Am. Mic. Soc., Vol. 

 18, p. 155, 1896. "The Rotifera of Sandusky Bay," by same. Ibid., Vol. 19, p. 43, 

 1897. "Rotatoria of the United States," by H. S. Jennings, Bull. U. S. Fish. Com. 

 for 1899, p. 67, 1900. "Synopsis of the Rotatoria," by same, Am. Nat, Vol. 35, p. 

 725. "Die Siisswasserfauna Deutschlands," Heft 14, 1912. "Index of the Rota- 

 toria," by H. K. Harring, Bull. 81, U. S. Nat. Mus., 1913. 



