189 
genus. In some species an enlargement of the anterior region of the 
body has been noted as due to the accumulation of egg-masses and 
embryos of the gravid female, but in N. tenellus this enlargement could 
not be the result of a mere physical effect of this nature since the same 
condition appears in males and in immature females also, The small 
number of individuals upon which the specific description was founded 
prevents an accurate determination of the limits of body size, and 
while the known limits are included within narrow bounds later study 
may alter these figures. The color of these small worms is translucent 
milky white. 
While the terminal hooks vary but little from those already de- 
scribed for N. emydis the size of the basal hooks is distinctly different. 
== 
E 
Figure 5. N. fenellus n. sp. Proboscis (X 145), hooks (X 465). Camera lucida 
drawing. 
The fact that the terminal hooks frequently exceed those of N. emydis 
in size while the basal hooks are constantly smaller than those of 
N. emydis precludes the possibility that the material upon which this 
species has been founded might be specimens of N. emydis whose 
growth had been retarded. The result of such a retardation in develop- 
ment would in all probability affect the various parts of the body 
equally so that if one row of hooks were smaller than normal the other 
rows on the same proboscis would in like manner be reduced. 
The cuticula and subcuticula are both slightly developed. The 
subcuticula is 0,015—0,025 mm. thick. The lemnisci have a length of 
about 0,87 mm., or over three times the length of the proboscis recept- 
acle, whose length is 0,26 mm. The brain is located in the middle of 
the base of the proboscis receptacle. The testes are oval in shape. In 
the specimens measured they are 0,21 mm. long with a width of 0,12 mm. 
The cement gland is 0,26 mm. long and 0,07 mm. wide. This gland 
empties its secretion into a cement reservoir of sac-like form as typical 
for other members of the genus. 
Two pickerel, Esox lucius Linn., taken from Lake Marquette at 
