REPORT ON THE CIRRIPEDIA. 17 



The Appendages. — As far as the number and the shape of the appendages of the 

 thorax are concerned, it has proved rather difficult to get any certainty; in the first place, 

 because the limbs with their thin chitinous wall refract the light in the same way as the 

 thorax, and are pressed so closely against the body of the thorax as to make it 

 impossible, even in a well-stained preparation, to make out their respective outlines, 

 and in the second place, because of the smallness of the parts in question. After a 

 careful study of sections, as well as from preparations made by dissection with needles, I 

 believe the following facts may be safely relied upon. Only four pairs of legs are 

 relatively well-developed; these are the four posterior pairs, and each of them is 

 composed of two branches. Of the first two pairs of cirri only one very short branch is 

 left. Each branch of the double-branched ones is relatively long and narrow, and 

 terminates in two or three very long spines. In a transverse section each leg is 

 represented by its chitinous wall and by the nuclei of its matrix, which are more or less 

 elongate (PI. I. fig. 5). 



The Cement-Glands. — Finally, I must describe in a few words the structure of the 

 cement-glands. They may be best studied in a section of a not quite full-grown specimen, 

 as shown in PI. IV. fig. 3. Each male contains a pair of these glands ; they are situated 

 a little above the vesicula seminalis (PI. I. fig. 1 c. gl.) ; they have an oval shape, and 

 measure about 0*15 mm. They are composed of very large cells with granular contents 

 and a large nucleus, kept together by an extremely delicate network of connective tissue 

 with a single rather small nucleus here and there between its fibres. Between the large 

 cement-cells cavities are left open here and there in the connective tissue ; each cell has 

 the shape of a wedge, and is placed so that the broader part is directed towards the 

 periphery, the narrower, on the contrary, towards the centre of the gland. The 

 structure of the contents of each cell is rather remarkable, since the larger granules 

 are placed at the periphery, and the contents are much more homogeneous towards the 

 narrower extremity of the cell. In one of the preparations the ducts which run from the 

 gland to the antennae were rather distinct ; they are attached as thread-like appendages 

 to one of the narrower extremities of the gland. 



Summary. — I think I have given herewith a full description of the so-called 

 complemental male of a species of Scalpellum. With this description, and with the 

 figures on Pis. I.— IV., it is possible not only to prove that this male has a highly degenerated 

 organisation, but also to demonstrate in what this degeneration consists, and how it affects 

 some of the organs very greatly, whilst others suffer less from it, and some are not influ- 

 enced by it at all. 



The state of things in the male under consideration may be summed up as follows : — 



1. The external characteristic shape of the species with its capitulum and peduncle, 



its valves and scales, is lost. The microscopic body consists of an elongate bag closed on 



(ZOOL. CHALL. EXP. PART XXVIII. — 1884.) Ee 3 



