524 FRESH-WATER BIOLOGY 



vagina present in adult. Male much smaller than female; with two spicules and accessory 

 piece. Females parasitic in body cavity of Teleostei. 



Single North American species recorded. 



Ichthyonema cylindraceum Ward and Magath. 



Male unknown, probably minute. Mature female loo mm. long, of nearly equal diameter 

 (0.48 mm.) everywhere. DeUcate, semi-transparent, and very fragile owing to thin body 

 wall. Lateral lines broad, light colored, conspicuous. No hps or papillae. Esophagus 1.09 

 mm. long, 0.066 mm. in diameter. Vulva and vagina atrophied, no vestiges discernable. 

 Female impregnated; uterus crowded with undeveloped ova almost spherical, 44 m in diameter. 



In abdominal cavity of Perca flavescens; Lake St. Clair. 



Fig. 817. Ichthyonema cylindraceum. Anterior end of female. X 35- (After Ward and Magath.) 



19 (18) Anus present in adult; vulva persistent in female. 



Family Filariidae Claus 1885. 



A large group not well known and imperfectly subdivided into a number of subfamilies, 

 leaving many other forms still unplaced. Most of the species are connective tissue parasites 

 and the majority inhabit terrestrial hosts. 



Forms that have not been described from this family exist in North American aquatic hosts. 

 Those recorded are few in number and imperfectly known. The following classification is 

 purely temporary. The genus Filar ia has been used as a convenient receptacle for all slender 

 roundworms that did not show conspicuous features of external anatomy adequate to place 

 them definitely elsewhere. Unless the proper location of a species could be determined clearly 

 it has been left imder this general heading even though its original location in this genus appears 

 to have been an error. 



Type genus FzYar/a 0. F. Miiller 1787 . . 20 



Among the forms recorded as "Filaria^' are some that have no usable description or in a 

 few cases none at all and must be recognized, if at all, by their host, habit, or geographic 

 location. Such are ^^Filaria ardearum" Stiles and Hassall 1894, cited from Ardea herodias, 

 in Leidy Collection. 



Filar ia atnphiumae Leidy 1856 encysted in the stomach wall of Amphiiima means; alcoholic 

 specimens in Philadelphia. 



Filaria cistudinis Leidy 1856 from the heart of Cistudo Carolina, Pennsylvania. 



Filaria spec. Leidy 1882, a red worm from the musculature and peritoneum of the black bass. 



Filaria nitida Leidy 1856 from Rana pipiens; later from fish and reptiles. "Probably 

 yoimg of F. solitaria." (Two species ?) 



20 (25) Anterior end without lips 21 



21 (22) Anterior tip lacks both lips and papillae. 



Filaria wymani Leidy 1882. 



No lips or papillae. Female 65 by 0.5 mm., sexual pore near center (?); viviparous. Eggs 

 0.02 mm. long; embryos 0.15 mm. Male half as large, with coiled caudal end; one spicule. 



Coiled on back of cerebrum of Plotus anhinga in Florida. Males rarer than females. Prob- 

 ably not Pelecitiis {Filaria) helicinus (Molin i860) with which Leidy later identified it. 



22 (21) Anterior tip with minute papillae 23 



23 (24) Oral papillae in two series of 4 to 6 each. 



Filaria solitaria Leidy 1856. 



Body cylindrical, rose-red with more deeply tinged extremities. Length up to 150 mm., 

 breadth i mm. Slightly narrower towards both ends. Tail obtuse; anus terminal, trans- 

 verse, with prominent lip. Esophagus tortuous, one-sixth length of body. 



Beneath dorsal skin of Rana pipiens; also in muscles of Anguilla chrysypa in Delaware 

 River. In peritoneum of Chelonura serpentina, Emys serrata, and Esox reticulatus. Most 

 frequent during winter and spring. Railliet thinks two species are involved. 



