16 
fied it in the genus Dithyridium as D. elongatum. In the meantime, 
however, Xeumann (1892a, 537-539, figs. 292-293) referred to the 
same parasite as ^^Plerocercoides hailleti^^^ clearly using a Latin bi- 
nominal nomenclature. 
The name Plerocercoides as used by Xeumann is traceable to Braun 
(1883a, 100) who used a German term (“ Plerocercoiden ’') to desig- 
nate certain larval forms which differed from the cysticercoids by 
having parenchymatous tails. As examples Braun cites a form which 
occurs in the body cavity of Trickodectes canis^ and the young {Gy- 
2 ?orhynchus of Tdenict macropeos and T. nnilatercdis. Blanchard 
(1888a, 491) used a French form {Plerocercoides) of the word, while 
Xeumann (1892a, 537) seems to have first used the Latin Plerocer- 
coides. From Xeumami's text, however, it is clear that he based his 
name on Braun’s “Plerocercoiden p hence Xeumann's Plerocereoides 
is not a generic name but the designation of an artificial collective 
group; hence also the type designation {bailleti) suggested by my- 
self in 1906 is not necessary under the new (1907) code. 
As a plerocercus may be the larval form of species belonging to 
widely distinct families, even to different orders, it is wise not to use 
the combination Plerocercus prolifer in case a better designation is 
available; this point probably occurred to Ijima, for he used the 
combination only once. Plerocercoides is also open to the same ob- 
jection, and in the only use of the term prior to Ijima it was used 
for a Dithyridium. 
It so happens that Diesing proposed a name Avhich is open to fewer 
objections. This is the 
Collective Group S-PARGANUM Diesing, 1850, 
Diagnosis. — Dihotliriocephalidx : An artificial collective group to contain 
larval stages of botlirioceplialicl worms wliicli have not reached a stage in 
their development that they can be determined generically. 
Such groups do not require a type species. 
In 1906 I placed Ijima’s form in this group as 
The Proliferating Japanese Tapeworm Larva — SPARGANUM PROLIFERUM 
(Ijima, 1905) Stiles, 1906. 
Specific diagnosis. — Sparganum: Larva may attain 1 to 12 mm. in length 
and 2.5 mm. in breadth ; head narrower and more motile than posterior end 
and may show an apical depression which, perhaps, serves as sucker ; no true 
suckers or other organs of attachment ]ire.sent. Calcareous corpuscles spherical 
or ellipsoidal, 7.5 to 12 /x (.Japanese worm) or 8.8 to 17.6 g, (Florida worm) 
in diameter, and situated in any part of body except head ; irregularly dis- 
tributed reserve food bodies present in older specimens, but they later undergo 
disintegration ; genital organs not present ; longitudinal muscles better devel- 
oped than either dorsoventral or transverse system ; transverse fibers do not 
