42 
THE VOYAGE OF H.M.S. CHALLENGER. 
diameter is about 0‘55 mm., its smallest 0T5 mm. I calculated that for Scalpellum 
regium the surface of the lumen of the oviduct was about 0 09 square millimetres, whereas 
a section of one of the nearly ripe ovarian eggs was not less than 0'28 square millimetres. 
Therefore, it is either necessary that the walls of the oviducts be very elastic, or that the 
eggs pass through the oviduct when it is much distended. Perhaps both circumstances 
favour the passage of the ova. 
The number of eggs laid by Lepas is immensely larger than by Scalpellum. In 
some of the species of the latter genus it is not even a hundred ; in Lepas anatifera it 
amounts, on the contrary, to many ' thousands and tens of thousands. In accordance 
therewith, the eggs of Lepas are very small ; I measured eggs from an egg mass of this 
species, and their length w T as only 0‘24 mm. The coeca which form the ovary are very 
narrow and elongate, and contain rows of numerous and relatively small eggs. The 
ovarian egg when ripe is not so elongate as after its fecundation ; I measured eggs in the 
oviduct, the length of which was only 0T4, their breadth being 0T mm. The nuclei of 
the eggs in the ovary are again nearly circular, and have a diameter of about 0'02 mm,; 
they may be seen as a rule in the centre of each ovarian egg, and contain a single very 
distinct nucleolus. In the coeca of younger specimens of this genus, the groups of 
ovigerms can be very distinctly made out. The number of ovigerms composing such a 
group in this genus, however, is much larger than in the genus Scalpellum ; their dimen- 
sions do not show any considerable difference. 
In Conchoderma virgatum the form of the coeca corresponds to that in Lepas. The 
eggs are numerous and small. I do not think it of much use to give any details as to 
their dimensions. 
When comparing young ovarian coeca, such as are observed in the peduncles of younger 
specimens, with those which are gorged with numerous and larger eggs, one feels 
convinced that a considerable increase in bulk has taken place. This can only have been 
brought about by a regular and abundant supply of food. Yet it is not so very easy to 
understand in what way the nourishment of the peduncle is brought about. The only way 
is, of course, that the blood — or the fluid which in Cirripedia acts as blood — passes through 
the narrow band which in the pedunculated Cirripedia runs from the capitulum to the 
peduncle, at the rostral side near the place where the two scuta meet with their occlu- 
dent margins. The two strong peduncular (antennal) nerves and the oviducts pass 
through this narrow commissure ; but so does also a rather wide cylindrical tube which 
has no distinct wall of its own, and therefore is lined only by connective tissue, and 
which here represents the body-cavity. In those cases in which I found the ovarian eggs 
ripe or nearly ripe, I always found this canal totally filled up by a delicately granulated 
mass, which much resembled blood plasma. I therefore think it highly probable that by 
means of this elongate canal a regular nourishment of the peduncle and the organs placed 
in it is carried on. In Scalpellum parallelogramma I have been successful in tracing 
