From the saccular portion, near the opening of this dilatation, springs the duct of the “prostate” (c). The wall of the “prostate” contains a network of branching and interlacing fibres. The “prostate” gland differs from that of S. brevis, Owen, where it is described as an “oblong, blind, glandular sac.” Loligopsis ocellata, Owen, too, shows a blind sac with a single duct for ingress and egress. Indeed this character seems common, so far as I have been able to discover; but the species at present under notice differs widely in having the “prostate” a thickened tube or canal with ingress at one end and egress near the other. The duct of the “prostate” (fig. 1 c) is slender, and has transparent walls. It leads to the receptacle of spermatophores, into which it opens near its upper end. The receptacle of spermatophores (b) is a large sac with thin transparent walls, and is usually packed with spermatophores and loose spermatozoa. It opens by a wide mouth into the penis (a) of whose base it appears to be a simple dilatation. The penis tapers gradually towards its opening, which has an uneven, almost fringed margin. When in sitû the vesicula seminalis and the duct of the “prostate” lie parallel to each other along the receptacle of spermatophores, to whose walls and to each other they are held by a membranous connection. The whorls of the prostate are held together by similar connections, so closely as to require the exercise of the utmost care to sever them without injury to the organ. The vesicula, duct, and receptacle of spermatophores thus held together lie transversely to the axis of the testis. Spermatophores (pl. vi., figs. 3–7).—A common length of the spermatophores is about 9 lines, but this is often exceeded. The shape varies somewhat, but the general outline is the same. One end is thickened, often club-shaped, or with a knob; from this end the spermatophore tapers, but as the opposite end is approached there is often a slight dilatation and the end is obtuse, never, so far as I have been able to observe, filamentous. The outer case is transparent and of tolerable consistency. The thick end is mainly occupied by a sac containing spermatozoa, which extends for varying distances, but seldom, if ever, half the length of the spermatophore. To this sac is attached a sponge-like body of definite though slightly varying shape, resembling the turned handle of an awl. This body fits into the spermatophoric tube like a piston. From it extends towards the thin end of the tube a flat spirally coiled thread enclosed in a transparent case. The thread may extend to the thin end of the spermatophore and be there attached, or it may extend nearly to the end and then be recurved, or it may not extend right to the end.