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TREMATODE GENUS BRACHYCOELIUM — BYRD 197 



genus Brachycoeliimh as described above. The definitive flame cell 

 pattern is known for all families now included in the superfamily 

 Dicrocoelioidea except for the family Lissorchidae. 



The members of the genus Brachycoelium, show a marked uniform- 

 ity in the characteristics of the definitive flame cell pattern. The 

 main variation noted for the system is in the irregularity of the 

 anterior end of the bladder stem. This end of the bladder may be 

 observed to end blindly as a knoblike projection beyond the origins 

 of the two common collecting tubules, or it may become somewhat 

 broadened and slightly notched so as to resemble the flame of an 

 oil lamp, at which times the common collecting tubules are given 

 off from the anterolateral angles of the bladder, or again it may 

 form short, bluntly rounded cornua, the tips of which give rise to the 

 common collecting tubules. It is probable that these variations in the 

 bladder stem are best explained by assuming that the bladder in 

 Brachycoelium is derived from the I-shaped bladder and that the an- 

 terior end of this is more elastic and allows for considerable expan- 

 sion. These variations in the stem of the bladder are of minor sig- 

 nificance as compared with the influence of the fundamental plan of 

 the excretory system. 



KEY TO THE SPECIES OF THE GENUS BRACHYCOELIUM 



1. Vitellaria in two groups, lateral to intestinal tract 2 



Vitellaria continuous from side to side in dorsal position, over- 

 lapping intestinal tract 9 



2. Body averaging 1 mm or less in length 3 



Body averaging more than 1 ram in length 4 



3. Testes anterior to ovary lynchi 



Testes posterior to ovary ovale 



4. Body averaging 4 mm long by 1.2 mm wide; European crassicolle 



Body averaging less than 4 mm long; American 5 



5. Vitellaria mediolateral, follicles united by a longitudinal vitel- 



line duct; worm 2.25 mm long; ratio of sucker sizes, 4:3 hospitale 



Vitellaria superficially placed, under ventral, lateral, or dorsal 



surface of body 6 



6. Vitelline follicles few in number, dorsally placed ; vporm 1 mm 



to 1.4 mm long ; ratio of sucker sizes, 2:1 to 8 : 5 trituri 



Vitelline follicles numerous, ventrally, laterally, and dorsally 

 placed 7 



7. Testes transversely oval, medially placed, their inner margins 



overlapping midline ; worm 1.7 mm long ; ratio of sucker 



sizes, 7: 5 mesorch.ium 



Testes elongated oval, lateral in position 8 



8. Testes large (more than 0.22 mm long) ; worm 1.3 mm long; 



ratio of sucker sizes, 2 : 1 georgianium 



Testes less than 0.22 mm long ; worm 0.75 to 1.4 mm long ; ratio 

 of sucker sizes, 5:3 obesum 



