(30 THE VOYAGE OF H.M.S. CHALLENGER. 



differing only in degree from those well-known and more conspicuous examples found 

 amongst the lower parasitic Copepoda and the Cirripedes. 



I observed in several cases — and this is noticed also by Claus — the attachment of 

 spermatophores to one of the fifth feet of the male (see PL XVIII. fig. 13, a). There can be 

 little doubt, I suppose, that this is the mode in which the fertilising element is trans- 

 ferred to the generative system of the female ; the spermatophores are quite commonly 

 seen affixed to the vulva. I have not noticed the club-shaped sensory appendages of the 

 anterior male antenna? which are figured and described by Claus, but though those organs 

 are frequently present in the males of most Calanoid Copepoda, their number and size are 

 extremely variable even in the same species. Indeed it seems to me very probable that 

 they are subsidiary sexual organs, adapted for some temporary purpose, and, that purpose 

 being fulfilled, that they — if the animal lives long enough — may drop off or become 

 atrophied. On the other hand, those males which are without them are probably, in the 

 majority of cases, individuals not yet arrived at sexual maturity. 



The genus is very widely distributed, indeed almost ubiquitous, except perhaps in 

 the Arctic and Antarctic, and in the colder parts of the temperate seas. The number of 

 species, however, seems to be small, several of those described by Dana being, as I believe, 

 founded upon different stages of growth of the same animal. The most conspicuous 

 generic characters are, in the female, the very long, scattered setse of the anterior 

 antennae, the absence of the fifth pair of feet, and the large doubly geniculated posterior foot- 

 jaws ; in the male, the long prehensile feet, the absence of the mandibles, and the absence 

 or atrophy of the first pair of foot-jaws. I strongly suspect that the notched rostrum will 

 be found to characterise one species only — Euchceta prestandrece. At airy rate the 

 genus as here denned includes some species which have neither that character nor the 

 single long caudal seta. 



1. Euchceta prestandrece, Philippi (PI. XVIII. figs. 7-15 (male), and PI. XIX.). 



? Eachmta prestandreie, Philippi, Archiv f. Naturgesch. (1843), Taf. iv. fig. 5. 



„ „ Claus, Die frei lebenden Copepoden, p. 183, pi. v. fig. 12, a, pi. ix. 



figs. 6, 7, 9, 12, pi. xxx. figs. 8-17. 

 „ communis, Dana, Proc. Amer. Acad. Sci. (1849) and Crust. U. S. Expl. Exped., 

 p. 1086, pi. lxxvii. fig. 1, a-e, and fig. 2, a-e. 

 ? „ eancinna, Dana, Crust. U. S. Expl. Exped., p. 1088, pi. lxxvii. fig. 4, a-b, and 



fig. 5, a-c. 

 1 „ pnbescens, Id. Ibid. p. 1090, pi. lxxvii. fig. 6, a-ij. 



„ atlantica, Lubbock, On some Entomostraca collected by Dr. Sutherland, Trans. Entom. 



Soc, voL iv. 1856, p. 13, pi. viii. 

 „ Sutherland) V, Id. Ibid. p. 14, pi. ix. figs. 1, 2. 



Length, l-8th to l-5th of an inch (3-5 mm.). Rostrum transversely notched 

 and forming two sharp teeth. Anterior antennae of the female rather longer than 



