44 THE VOYAGE OF H.M.S. CHALLENGEE. 



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 cirras in SccdpeUum is different from Lepas. In Scalpellum vulgare (PL VI. 

 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 curiotis sack which opens at the base of the sweUing. 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 Scalp)ellum, 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 oi 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 VI. fig. 11), I have 

 given up this supposition, which I must confess was rather hazardous. 



The structure of the cells Mdrich compose the wall of the curious sack is that of a high 

 cylindrical epithelium. In Scalpellian 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 

 0"006 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 Sca^jellum 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 rel-atively 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 Scalpelhim in which I inyestigated this curious sack 

 did I find it ermpty {Scalpellum vulgare, Scalpellum parallelogramma, Scalpellum nympho- 

 cola, Scalpellum regium, a^d Scalpellum halanoides have been investiga,ted bj^ means of 



