268 ANIMAL COLOKATION. 



laden with ova or milt, wliicli was discharged in little thin 

 milky streams, one from each side of the body, as they swam 

 through the water. The reproductive elements commingling 

 under these conditions were fertilised after the manner of the 

 spawn of certain fishes." 



These facts are evidently of the highest importance in 

 estimating the value of the theory of sexual selection. It has 

 been shown that at the epoch of sexual maturity these worms 

 indulge in unusual antics and gyrations, which cannot captivate 

 either sex as there is no pairing, but merely a fortuitous 

 concurrence of the sexual elements shed into the sea. 



As a general rule, sexual dimorphism is not found among 

 inactive animals low in the scale ; but there are plenty of 

 exceptions. The " complemental males " of the Cirripeds and 

 the parasitic male of the Gephyrean Bonellia are examples ; 

 there can be no question here of female likes and dislikes. 



More positive facts are quoted by Mr. Wallace*: "Some 

 peahens preferred an old pied peacock; albino birds in a state 

 of nature have never been seen paired with other birds ; a 

 Canada goose paired with a Bernicle gander ; a rush widgeon 

 preferred a pintail duck to its own species ; a hen canary pre- 

 ferred a male greenfinch to either linnet, goldfinch, siskin, or 

 chaffinch. . . . Messrs. Hewitt, Tegetmeier, and Brent, three of 

 the highest authorities, ' do not believe that the females prefer 

 certain males on account of the beautv of their plumage.' . 



i/ J. O 



Evidence is adduced that a female pigeon will sometimes take 

 an antipathy to a particular male without any assignable 

 cause; or, in other cases, will take a strong fancy to some one 

 bird, and will desert her own mate for him ; but it is not 

 stated that superiority or inferiority of plumage has anything 

 to do with these fancies." 



* " Darwinism,'" p. 285. 



