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Within the genus Neorhynchus the writer has found the number of 
nuclei in any given organ or region of the body is fixed for each species. 
The results of a detailed study of cell-constancy in members of this 
genus will appear soon. Certain points in this matter of constancy of 
numbers of nuclei hold for every member of the genus. This last fact 
has led me to propose an emendation of the characters diagnostic for 
the genus Neorhynchus, which are, as I conceive them; 
1) the subcuticula contains six giant nuclei arranged, normally, 
five in the mid-dorsal line of the body and one in the mid-ventral line; 
2) one lemniscus contains two giant nuclei, the other a single one; 
3) the wall of the proboscis receptacle contains but a single layer 
of muscle. 
In the Neorhynchi clearly marked specific characters such as might 
serve for a ready determination of species are extremely few. Body size 
is such an unstable. quantity that very little taxonomic value may be 
given it. The most sharply defined diagnostic points of value are: the 
number, shape, and size of the hooks upon the proboscis; and the shape 
and size of the embryos within the body of the mature female. The 
difficulties encountered in interpreting descriptions giving the length of 
hooks without specifying how the measurements were taken, have led 
the writer to insert here the statement that in all his measurements 
the length of the hook is taken to be the longest straight line from the 
tip of the hook to the union of the hook with its basal portion or root 
(figs. 1 and 3 a—b). 
Neorhynchus gracilisentis n. sp. 
Body small, subcylindrical, slightly tapering at either end, bent 
into a slight crescent. Fully mature females 1,7—4,0 mm. long, greatest 
breadth slightly anterior of middle, 0,38 mm. Males 1,5—3,0 mm. long, 
greatest breadth about 0,30 mm. Proboscis short, slightly longer than 
wide when fully extended, largest at tip, tapering toward base to region 
of basal row of hooks where abrupt change in diameter occurs; armed 
with three circles of twelve hooks each. Hooks all delicate, terminal 
row curved, 0,015—0,017 mm. long, root long, — 0,020 mm.; second. 
row curved but less than first, 0,012—0,015 mm. long, root long; third 
or basal row slightly curved, 0,015—0,020 mm. long, without pronounced 
root. Embryos conspicuously spindle-shaped, 0,036—0,040 mm. long 
by 0,010 mm. broad. 
In general the females are larger than the males for although in 
this species the upper and lower limits of size are very nearly uniform 
for the two sexes yet greater numbers of individuals among the females 
are found near the upper limit, while among the males there is a ten- 
