Hawaiian Polyclads — HymAN 
333 
rounded by dense mesenchyme, and after 
bending dorsally terminates in a slightly ex- 
panded chamber housing the elongated, con- 
ical penis papilla. The central duct of the 
papilla, or ejaculatory duct, proceeds forward 
and downward very sinuously and becomes 
continuous with the central part of a tripartite 
seminal vesicle. This has pronounced muscu- 
lar walls of chiefly circular fibers. It is very 
peculiar in that one horn of this tripartite 
structure descends ventrally, receiving one 
sperm duct, and the other ascends dorsally, 
receiving the other sperm duct. This lack of 
bilateral symmetry in the entry of the sperm 
ducts into the seminal vesicle is certainly very 
unusual. Possibly the two horns of the tripar- 
tite seminal vesicle should be regarded as 
spermiducal bulbs, that is, as thickened term- 
inations of the sperm ducts. 
The female gonopore leads into a short, 
expanded antrum from which the vagina pro- 
ceeds forward and then dorsally in a very 
sinuous manner, not indicated in the figure. 
Shortly after bending from a vertical to a 
horizontal position, the vagina receives the 
common oviduct and then continues as an 
oval Lang’s vesicle. The female tract through- 
out has a well-developed muscular coat of 
mainly circular fibers. The same peculiar asym- 
metry seen in the entry of the sperm ducts 
into the male apparatus also obtains in the 
entry of the oviducts into the vagina. As 
shown in Figure lb, one oviduct is situated 
ventrally, the other dorsally. Cement glands 
were not evident, no doubt because of the 
poor histological condition. The uteri also 
could not be traced anteriorly. 
A penis papilla at the inner end of a long 
male antrum guarded distally by a penis 
sheath also characterizes two other species of 
Euplana—concolor Meixner, 1907, and clipper- 
toni Hyman, 1939. However, a penis stylet is 
present in the latter, and the Lang’s vesicle is 
very small in the former. Further, no other 
species of Euplana has the peculiar asym- 
metry of the sperm ducts and the oviducts 
that distinguishes E. tropicalis. 
The holotype has been deposited in the 
United States National Museum in the form 
of slides bearing the anterior half mounted 
whole and the copulatory complexes as sagit- 
tal serial sections. 
Family PLANOCERIDAE 
Paraplanocera oligoglena 
(Schmarda) 1859 
One specimen of this species, collected by 
H. W. Henshaw at Hilo, Hawaii (no date), 
was sent as a whole mount. The specimen 
was much ruffled, measuring 33 millimeters 
in length by 28 millimeters in breadth. The 
features of the copulatory apparatuses, in- 
cluding the two large teeth at right angles to 
each other in the cirrus sac, were readily seen 
in the whole mount and considered to es- 
tablish the identification without the necessity 
of sections. This species is cosmopolitan in 
tropical and subtropical waters and has been 
recorded from a number of localities in the 
Indo-Pacific region, further from the Gulf of 
California (Hyman, 1953^.' 353-357). The 
whole mount has been returned to the U. S. 
National Museum. 
Planocera pacifica n. sp. 
Figs. 2, 3 
A fine, perfect specimen was taken in the 
Hawaiian Islands by P. S. Galtsoff, July 27, 
1930, in the evening, hence presumably swim- 
ming at the surface. The specimen (Fig. 2) 
is of broadly oval form, with ruffled margins, 
40 millimeters long by 25 millimeters wide. 
The color is indeterminable, but the worm 
appears thin and transparent. There is a pair 
of conspicuous conical tentacles near the 
brain, far back from the anterior margin. A 
ring of tentacular eyes occurs at the base of 
each tentacle. The fairly numerous, small cere- 
bral eyes (Fig. 3^) are more abundant anterior 
to than behind the brain level. The broad, 
ruffled pharynx with about six main lateral 
folds on each side occupies approximately the 
central region of the worm (Fig. 2), and di- 
