COPEPODA. 399 



more remarkable is, besides the minute size of the animals, 

 the fact that the structure of the eyes is so simple that it appears 

 inconceivable that their owners should be in any degree aware 

 of the ornamentation presented by their fellows. In some 

 species both sexes are similarly ornamented (e.g. Augaptilus 

 filigerus, Glaus), in others the male alone is brilliantly coloured 

 (Sapphirina), but in several of the most marked instances it is 

 the female which is conspicuously decorated (Calocalanus, 

 Copilia) while the males are comparatively plain. Some details 

 of the ornamentation are given below under the separate families. 



In contrast with this kind of dimorphism is that found among 

 the parasitic Copepods. While in some families the sexual 

 differences are slight, in Lernaea (as the result of fertilization) 

 and in the Chondracanthidae and Lernaeopodidae (indepen- 

 dently of that event, Fig. 265) the female grows to a large size, 

 acquiring a monstrous, distorted appearance in which its Copepod 

 characters are completely masked, while the minute males, 

 dwarfs in comparison, retain more of their original characters and 

 frequently live, attached by their hooked appendages to the 

 body of the female. 



The testes and vasa defer entia may be single or paired. The 

 spermatozoa are elongated bodies twisted about their long axis. 

 They are contained in spermatophores, which are formed in the 

 lower part of the vas deferens. During copulation, which is 

 only an external approximation of the two sexes, the male 

 fastens one or more spermatophores on the genital segment of 

 the female. The ovary, like the testis, may be single or paired, 

 but the oviduct is always paired. A cement gland is generally 

 present at its termination which also performs the office of a 

 spermatheca where this organ is not separately developed. A 

 separate duct, to the orifice of which the spermatophore is at- 

 tached by the male, leads into the spermatheca (or cement gland). 

 Through this the spermatozoa are injected by the expansion 

 (owing to the inhibition of water) of a fluid contained in the 

 spermatophore. The eggs are fertilized in the lower end of the 

 oviduct, and a mass of them becomes enveloped in the secretion 

 of the cement glands, which hardens in the water. The egg 

 sacks so produced are single or paired, and may be oval or fili- 

 form (Figs. 257 and 266, d). In some cases however the eggs 

 are laid singly, and in the Notodelphyidae they develop in the 



