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



all sides. A very small slit represents the opening between the two scuta. The 

 antennse are the only extremities which still show their original condition ; the cirri 

 have grown straight and functionless ; the parts of the mouth have disappeared. 



2. The cement apparatus is well developed as long as the male is young ; when 

 mature it is no longer so distinct. 



3. The intestine has become functionless and is quite rudimentary ; circulatory and 

 respiratory organs may be passed by, as they have no distinct organs even in the herma- 

 phrodite Scalpellum. 



4. The nervous system consists of a relatively small supra -oesophageal ganglion, of a 

 not. very stout oesophageal ring, and of a large thoracic ganglion. It is probably the 

 latter which alone regulates the functions of the genital apparatus. The peripheral part 

 of the nervous system is not much developed. The eyes (and other organs of sense) have 

 been lost. 



5. The genital apparatus is the only well-developed system of organs. The female 

 apparatus, however, is totally lost, and even the male organs show a great deal more 

 concentration than do the same organs in ordinary hermaphrodite Cirripedia. In the 

 first place the testis is single, and has become a rather compact gland, whereas in other 

 Cirripedia it is double and scattered throughout almost the whole interior of the body. 

 In the second place, the vesicula seminalis is also represented by a single vesicle only, 

 hermaphrodite Cirripedia on the contrary having always two of them. 



In all these respects the little males of other deep-sea species of Scalpellum which I 

 have been able to investigate exactly correspond to the male of Scaljjellum regium. 

 So does the male of Scalpellum vulgare (from specimens from the Mediterranean) with 

 the exception of the presence of rudimentary valves, which in that species, as in some of 

 the deep-sea species {vide p. 4), represent the so-called primordial valves of the young 

 capitulum of pedunculated Cirripedia. 



c. General Observations. 



In the case of Scalpellum vulgare, Leach, Scalpellum rostratum, Darwin, Scalpellum 

 peronii, Gray, sp., and Scalpellum villosum. Leach, sp., Darwin observed what he 

 considered a penis ; in Scalpellum vulgare. Leach, and in Scalpellum villosum. Leach, 

 sp., he ascertained moreover the presence of vesiculse seminales and testis in the 

 specimens which were also furnished with ovaria. These specimens, therefore, were 

 hermaphrodites, and as little males were found attached to their scuta, these male 

 specimens got the very characteristic name of " complemental " males. On the other 

 hand Scalpellum ornatum, Gray, sp., did not show a trace of a proboscidiform penis 

 hi the four specimens which Darwin examined, and he, therefore, supposes that the 

 animab studied by him were females, although it was impossible, as the specimens were 



