392 FRESH-WATER BIOLOGY 



84 (91) Uterus between ovary and acetabulum, possessing an ascending 



ramus only. Testes ordinarily behind ovary and close to 

 it, or rarely (Leuceruthrus) near acetabulum and separated 



from ovary by coils of uterus 85 



In Deroprislis hispida, a peculiar distome found in Acipenscr in Europe and reported once 

 by Stafford in the lake sturgeon from Canada the arrangement of the germ glands differs from 

 either plan noted in the key line above. Two oval testes are median in posterior end; median 

 ovary lies near large receptaculum, separated from acetabulum and testes by about equal 

 distances which are filled by uterine coils. Uterus has short descending ramus which extends 

 posteriad from ovarian complex to anterior testis, and long ascending ramus from this point to 

 genital pore on median anterior margin of acetabulum. Vitellaria are extracecal, in uterine 

 region. Cirrus sac and seminal vesicle, nearly median and postacetabular, are both well de- 

 veloped, but rather distinctly separated. The relationship of the genus is not clear and the 

 American record needs confirmation, hence this form is not included in the key. 



85 (88) Body muscular; cirrus sac present. 



Family Azygiidae Odhner 191 1 . . 86 



Infra-medium to large distomes. More or less elongate, flattened, with thick, muscular 

 body. Suckers powerfully developed. Skin smooth, on contraction drawn into irregular 

 transverse folds. No prepharynx. Pharynx powerful, esophagus very short, intestinal crura 

 reach posterior end. Excretory bladder Y-shaped with very long branches reaching even to 

 anterior end. Genital pore median, in front of and above acetabulum; genital sinus spacious. 

 Uterus with ascending limb alone, extending direct from ovary to genital pore in closely laid 

 transverse loops. Laurer's canal present; receptaculum seminis wanting. Vitellaria follic- 

 ular, lateral, extracecal, not reaching to posterior end. Eggs 45 to 8s ii long, with cap; when 

 deposited they contain each a ripe embryo, regularly nonciliated. 



Stomach parasites of fishes. 



86 (87) Germ glands form series in posterior region; ovary anterior, not far 



separated from testes Azygia Looss 1899. 



Distomes of moderate size or larger, with slightly flattened, much elongate, nearly cyhndri- 

 cal muscular body, rounded at both ends (Fig. 632). Genital pore close to acetabulum. Cirrus 

 sac present. Seminal vesicle long and coiled. Uterus intercecal, in center third of body. 

 Vitellaria extend at least between acetabulum and posterior testes. Ovary and testes behind 

 middle of body. Main stem of excretory bladder splits behind testes; lateral branches do not 

 unite in anterior region. Eggs 43 by 21 11 with thin shell and albumen covering. 



Azygia is a powerfully muscular type and is usually much distorted in the process of preser- 

 vation so that a lot of specimens taken from the same host at the same time present marked 

 external differences in the preserved condition. Such extreme specimens have been the basis 

 for various new genera, e.g., Megadistomum of Leidy and Stafford, Mimodistomum of Leidy 

 tnd Hassattius of Goldberger. The same factor has led to the separation of too many as species. 



Despite many records of its occurrence the common European A . lucii ( = A. tereticolle) has 

 not been found in North America. Several species peculiar to this continent occur in A mia calva, 

 Micropterus salmoides and dolomieu, Esox lucius and reticiilatus, Ambloplites rupeslris, Salw- 

 linus namaycush, Lucioperca, Lota lota, Salmo sebago. Maine, St. Lawrence, Great Lakes, 

 Wisconsin. 



87 (86) Testes just behind acetabulum, separated from ovary by coils of 

 uterus. . Leuceruthrus Marshall and Gilbert 1905. 



Anterior end rormded, posterior end pointed. Oral sucker ventral, promi- 

 nent, acetabulum one-half as large. Intestinal crura slender, straight, ex- 

 tending nearly to posterior end. Excretory vesicle forking at ovary. Testes 

 small, postacetabular, oblique to each other. Uterus at first confined to area 

 between intestinal crura, ovary and testes, later filling posterior three-fourths 

 of body. Vitellaria lateral, in posterior half of body. Laurer's canal present. 



One species known (L. micropteri) from mouth and stomach of black bass 

 and bowfin in Wisconsin and Indiana. 



Odhner advocates the association of this genus with Azygia from which 

 It differs primarily only in the fact that the testes have moved from their 

 original place behind the ovary and have been drawn anteriad by the 

 shortening of the sperm ducts to a location a little posterior to the acetabu- 

 lum. This IS the relation they hold in Hcmiurus, marine distomes descended 

 from the Azygiidae. 



Fig. 679. Leuceruthrus microplerl. Ventral view showing internal topography. 

 After a press preparation. Very slightly diagrammatic. Magnified. (After Gold- 



