44 
THE VOYAGE OF H.M.S. CHALLENGER. 
the limits of the cells are never very distinct, and their height is inconsiderable ; the 
contents of the cell are a nucleus about 0’005 mm. in diameter and quite clear protoplasm. 
A very thin membrana propria covers the outer surface of the oviduct. 
The way in which the oviduct corresponds with the sack in the basal articulation 
of the first cirrus in Scalpellum is different from Lepas. In Scalpellum vulgare (PI. YI. 
fig. 10), and Scalpellum parallelogramma, the oviduct, once arrived in the basal articula- 
tion, expands so as to form a kind of funnel, which with its wide opening embraces a large 
portion of the curious sack which opens at the base of the swelling. The wall of this 
funnel closely resembles that of the oviduct. In some of my preparations the funnel is 
placed exactly opposite to the genital opening, in others it is attached to the sack in a 
more oblique direction. The curious sack, in Scalpellum, communicates with the genital 
opening by means of a long duct, the length of which equals and sometimes even surpasses 
that of the sack itself. At the other extremity the sack is open also and its wall round 
about the opening turned outward, the opening of the funnel closing exactly on the margin 
of the part which is turned out. In one of my series of preparations of Scalpellum vulgare 
the funnel-shaped widening of the oviduct is in close relation with a bag of connective 
tissue surrounding the whole sack, so that it may be traced up to where the sack goes 
over into the duct ; at first it was my opinion that the eggs passing through the oviduct 
and the funnel arrived in this bag and then passed into the duct by a lateral opening 
situated beneath the sack, without entering the curious sack at all ; but I failed to 
make out the existence of this opening, and since I afterwards observed the direct 
transition of the oviduct into the curious sack in the genus Lepas (PL YI. fig. 11), I have 
given up this supposition, which I must confess was rather hazardous. 
The structure of the cells which compose the wall of the curious sack is that of a high 
cylindrical epithelium. In Scalpellum vulgare their dimensions are 0'02 by 0‘006 mm.; 
each cell has a very distinct oval nucleus which, in the full-grown specimens, measures 
O’OOG by 0'005 mm., and which is seated very close to the free extremity of the cell. 
The outer surface of the sack is lined by a membrana propria with very flat nuclei. The 
shape of the sack in Scalpellum is that of a pear, the part which communicates with the 
duct being as a rule narrower than the other extremity. In Scalpellum vulgare the duct 
shows a small swelling near the place where it communicates with the sack, and the 
length of the duct is exactly equal to that of the curious sack. The wall of the duct 
has the same structure as the outer wall of the body, as an inflected part of which it 
must be necessarily considered. The limits of the cells which compose it are not distinct, 
its nuclei are relatively oval and large, their longest diameter being 0'009 mm. The 
surface of the duct is covered by a thin chitinous cuticle. 
In none of the species of the genus Scalpellum in which I investigated this curious sack 
did I find it empty {Scalpellum vulgare, Scalpellum parallelogramma, Scalpellum nympho- 
cola, Scalpellum regium, and Scalpellum balanoicles have been investigated by means of 
