REPORT ON TITE CIRRIPEDIA. 17 



Copepoda (Grobl)en) are never observed in the Nauplius of the Cirripedi;i; tin- lateral 

 horns and the very complicated system of dermal glands of the latter are again wanting 

 in the Copepod- Nauplius. The various spinous processes of the Cirriped-Nauplius in 

 the larva of the Copepoda are sought for in vain. No doubt a great many of these 

 differences may be caused by adaptive changes, and be considered as secondarily acquired 

 protective organs, as Balfour ' calls them — yet this is also a supposition of a somewhat 

 speculative character. 



Moreover, we must not lose sight of the fact that it will always be very difficult to explain 

 why the Cypris-stage, so highly characteristic of the ontogeny of the Cirripedia, is totally 

 wanting in the development of the Copepoda, and why, when we consider an Archi- 

 phyllopod as the common ancestor of both groups, the Copepoda, which are developed 

 from it in a much more direct way, should be unisexual, whereas the Cirripedia, as 

 a rule, are hermaphrodite. Claus himself has pointed out this latter difficulty,' 2 and tries 

 to explain it by submitting that the hermaphroditism of the Cirripedia is of a secondary 

 character. This supposition in the first place is based on the fact that the Cirripedia arc 

 not exclusively hermaphrodite, and in the second place, that in those cases in which 

 unisexuality is observed in the group of the Cirripedia, it occurs in a stage which 

 corresponds to the Cypris-stage of the ordinary development ; a younger stage corre- 

 sponding to an earlier period of the phylogenetic development. As this latter 

 conjecture is based in the first place on the sexual relations of the different forms of 

 Scalpellum, with which I shall have ample occasion to deal when describing the numerous 

 species of that genus collected during the cruise of H.M.S. Challenger, a discussion of this 

 point may be postponed till then. 



An elaborate discussion of what had been published on the so-called Cirripedia 

 Suctoria, or Rhizocephala, does not be within the province of this Report. As not a 

 single specimen of a Sacculina or a Peltogaster is to be found in the Challenger col- 

 lection handed over to me, and as my inquiries of the gentlemen engaged in preparing 

 reports on the Crustacea Podophthalmata, Brachyura, Anomura, &c. — the animals 

 on which the parasitic Cirripedia are found living — have proved in vain, it seems that 

 not a single representative of this group was taken during the cruise of H.M.S. Chal- 

 lenger. 3 Considering that Prof. Semper, during his stay in the Philippine Archipelago, 

 collected nineteen different species of this group, it seems rather curious that not a single 

 specimen was taken by the Challenger. The only way to explain it would be, that the 

 Crustaceans living in shallow water in the neighbourhood of the coast are not very richly 

 represented in the Challenger collection, and that the Cirripedia Suctoria at present 

 known were taken, almost without an exception, from such shallow-water inhabitants. 



1 Balfour, Larval Forms, Quart. Journ. Micr. Sci., vol. xx. p. 381, 1880. 



2 Claus, Genealogische Grunilla^e., p. !M>, >i *«/. 



3 See note by the Editor of the Reports, p. 19. 



(ZOOL. CUALL. exp. — part xxv. — 1883.) Bb 3 



