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lemnisci are straight sacs about one sixth to one fourth the length of the 
body cavity. The proboscis receptacle in a full grown individual is about 
0,45 mm. long. The muscle layer of which its wall is composed has a 
thickness of 0,032 mm. In the middle of the base of this receptacle is 
located the brain, a conical mass of tissue the apex of which is directed 
cephalad. 
The two testes are crowded closely together. The anterior one is 
usually the larger, 0,70 mm. long by 0,26 mm. wide, while the posterior 
testis is but a little smaller. The cement gland is a very much elongated 
rectangular mass of tissue which fills the greater part of the body cavity 
just posteriad to the hind testis. It has a length of 1,05 mm. The reser- 
voir of this gland is about 0,035 mm. long. 
In no case has a female of this species been found in the stage 
before the breaking up of the ovary. The embryos show but slight. 
deviation from the ordinary dimensions of 0,049 0,021 mm. The 
genital opening is ventral and subterminal. 
The material upon which this species has been founded consists of 
forty-one mature individuals from the black-bass, Micropterus salmoides 
(Lacép.) at Pelican Lake, Minnesota. For this material the writer is 
indebted to Dr. George R. La Rue. Materials received also from Pro- 
fessor Linton and identified by him as probably » Echinorhynchus 
agilis« have proved to be of the species N. cylindratus. This makes it 
necessary to include the eel, in the vicinity of Woods Hole, Mass., 
among the hosts of this parasite. Since all the specimens the writer has. 
seen.are fully mature it is not possible to present any data concerning 
the period of infestation. 
Neorhynchus tenellus n. sp. 
Body small, both ends strongly curved toward ventral, posterior 
half or two thirds noticeably attenuated. Females 3,5—5 mm. long, 
maximum breadth 0,280 mm. Males 2 mm. long, maximum breadth 
0,280 mm. Proboscis short, cylindrical, length about 0,150 mm., breadth 
0,135 mm. Three circles of hooks, six in a circle. Hooks in adjacent. 
rows alternating. Terminal hooks 0,090—0,110 mm. long, middle row 
0,038 mm. long, basal row 0,027 mm. long. Embryos not found in any 
of specimens examined. Egg-masses small, 0,043 X 0,027 mm. 
The body form of this species is so strikingly different from that 
found in other Neorhynchi that while the writer is loath to attribute 
any marked value to body form and size as diagnostic characters at least 
in this instance it seems necessary to make mention of the characteristic 
attenuation of the body in the posterior region as contrasted with the 
more nearly uniform body diameter found in other members of the 
