PAIRING, COURTSHIP, AND PARENTAL CARE 299 



of notice. In the great majority of Bony Fishes the females are 

 larger than the males, and in some Cyprinids she may be as 

 much as six times as large as her mate, whilst in certain Gyprino- 

 donts the disparity in bulk is even more marked. In some 

 fishes, however, of which the Cod, Haddock {Gadus), and 

 Angler (Lophius) may be mentioned, the males are slightly the 

 larger. One of the commonest of the secondary sexual differ- 

 ences in fishes is concerned with the coloration of the body and 

 fins, the males almost always having a brighter livery than 

 their mates. This is the case in nearly all the Cyprinodonts, 

 Cichlids, Labyrinthic-fishes, many Damsel-fishes (Pomacentridae) , 

 Wrasses (Labridae), and so on {cf. p. 223). Blue, red, green, 

 black, and silvery-white pigments are especially characteristic 

 of the males, whereas the females generally exhibit dull, oli- 

 vaceous, or variously mottled hues. In some fishes, notably in 

 some of the Wrasses {Labridae) and in the Dragonets [Calliony- 

 midae), not only are the colours different, but also the character- 

 istic markings. In our own Cuckoo Wrasse [Labrus mixtus), to 

 mention only one example, the male is yellow or orange tinged 

 with red, with five or six blue bands radiating backwards from 

 the eye; the fins are yellow or orange, with a large blue blotch 

 on the front part of the dorsal fin. The female is reddish, 

 there are no blue bands, but two or three large black spots are 

 present on the back, below the hinder part of the dorsal fin. 

 In many of the Cyprinids the males become much brighter 

 during the spawning season, chiefly through the development 

 of bright red or blue pigment, especially in the lower parts of 

 the body, and these colours may become very much intensified 

 during the actual courtship, with its attendant emotional 

 excitement. In the little Three-spined vStickleback (Gasterosteus 

 aculeatus) both sexes change their colours in the breeding-season, 

 the dark greenish colour of the back extending on to the sides 

 in the form of vertical bars, whilst the lower parts change from 

 a silvery white to pale yellowish in the female and a brilliant 

 red in the male. In the Ten-spined Stickleback (G. pungitius) 

 the males change from a greenish-olive powdered with small 

 black dots to a dark brownish. Among other changes in livery 

 that of the breeding Salmon {Salmo) has already been described 

 [cf. p. 284), and there are other examples too numerous and 

 varied to be mentioned in detail here. The male Bow-fin 

 (Amia) of North America may be recognised quite readily by 

 his smaller size and by the presence of a deep black spot ringed 

 with white at the base of the caudal fin, which, although present 



