/42 THE VOYAGE OF H.M.S. CHALLENGER. 



diameter is about 0'55 mm., its smallest 0"15 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 circumstailces 

 favour the passage of the ova. 



The number of eggs laid by Lepas is immensely larger than by Scalpelhim. 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 was 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 0'14, their breadth being 0"1 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 virgattim 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. traciifg 



