8 THE VOYAGE OF H.M.S. CHALLENGER. 



body is visible which, I think, must necessarily represent the cement-gland. However, 

 neither the place it occupies nor its structure shows any resemblance to the same glands — 

 or what we must consider as such — in the Cypris of Lepas australis. Nor have these 

 glands in the male of Scalpellum regiumgce&t conformity with those organs in the younger 

 Cypris-stage of another species of Scalpellum (Scalpellum triangulare), which I figure in 

 PI. II. fig. 4. In this stage the antenna; (An) are still totally hidden within the valves, 

 and the cement-glands (C. gl) form very large cellular masses situated on both sides of the 

 thoracic part of the body between it and the valves. I think it is in this stage that the 

 Cypris-larva leaves the mantle cavity of the mother. 



What we called the mantle in the Cypris of Lepas australis takes in the male Cypris 

 of Sen! pi II a, ,i rvgiiun the form of a bag closed on all sides, with only a very small opening 

 at the hinder extremity. This opening no doubt corresponds to the slit-like opening at 

 the ventral side of the ( lypris of Lepas. It also serves the same purpose. We see the 

 very delicate and slender spines placed at the extremity of the legs come forth from this 

 opening. For want of material I have not been able to study in detail the structure of 

 the mantle, nor its musculature. I can only say that the mantle is composed of 

 flat and pale rounded cells of 0"01 mm. in diameter, with a small clear nucleus, and that 

 these cells are placed at a little distance from each other; that the muscular fibres form 

 a single layer only, and are built up of elongate oval cells placed in longitudinal rows and 

 each furnished with a distinct nucleus (PI. I. fig. 7). Besides the body the interior of 

 the mantle contains a mass of connective tissue with little grains and small fatty corpuscles 

 scattered irregularly throughout its meshes. With regard to the body it is not difficult to 

 observe the mouth (PI. II. fig. 3, M), the oesophagus ((E), and the stomach (St); the 

 nervous system consisting of a supracesophageal ganglion (G S) and a single, rather large 

 thoracic ganglion (G T) ; six pairs of very slender cirri with delicate spines at their 

 extremities; ;i pair of long and well developed caudal appendages (C A). A dark 

 coloured mass, consisting for the most part of yolk-fragments, makes up a great deal of the 

 rest of the true body of the embryo Scalpel/inn. 



As for details, I can only say that the parts which surround the mouth are not very 

 distinct, and that the very long oesophagus leads into a blind pouch of an oval shape, and 

 that this pouch represents the stomach. The two branches of each cirrus are indistinctly 

 divided into (bur segments; the shape of each segment is cylindrical, with the exception of 

 the last joint, which is conical, and slopes into the very long spines placed at the extremity. 

 The first two pairs of cirri are somewhat different from the following pairs, inasmuch as in 

 the first two the lower two segments are the only ones which are filled up with a mass of 

 cellular structure; so, when the cirri have shed the exuviae which now cover them, the 

 cirri of the first two pairs undergo a considerable diminution in Length. The very long 

 caudal appendages in this stage are also represented only by the chitinous skin. After 

 the last casting of skin they will no doubt have disappeared. 



