PAIRING, COURTSHIP, AND PARENTAL CARE 301 



first few rays of the dorsal fin, as well as some of the rays of the 

 pelvics, are prolonged to form more or less lengthy filaments in 

 the male; in the closely related genus Bothus the males 

 are provided with spines on the snout and have the eyes much 

 wider apart than the females, while the upper rays of the 

 pectoral fin of the coloured side are frequently very elongate 

 (Fig. ioqb). The Sword-tailed Minnow {Xiphophorus) from 

 Mexico and Central America, a favourite Gyprinodont for the 

 aquarium, has the lower lobe of the caudal fin drawn out to 

 form a long blade-like filament in the male, and in another 

 member of the same family {Mollienisia) the dorsal fin is enlarged 

 in the male to form a relatively huge, sail-like structure marked 

 with brilliant ocelli. 



Among the characteristic peculiarities of the males, developed 

 only as the breeding season approaches, the horny tubercles 

 on the head and body of many Cyprinids, and the hooked jaws 

 and enlarged teeth of the Salmon have already been described 

 {cf. pp. 92, 284). Many male Cichlids {Cichlidae) develop a 

 huge fleshy hump on the forehead, which is gradually reabsorbed 

 after spawning in some species and retained throughout life in 

 others. Other Cichlids develop a much branched structure 

 in the region of the vent, brilliantly coloured, generally with 

 scarlet. It has been supposed that this is used for brushing the 

 milt on to the ova, but its ornate appearance suggests that its 

 function may be partly decorative. In the male of the South 

 American Lung-fish {Lepidosiren) the pelvic fins are covered ^ 

 during the breeding season with bright scarlet processes, richly 

 supplied with blood-vessels {cf. p. 305). 



The courtship of the female by the male may consist merely 

 in swimming round and round in her vicinity, betraying a 

 varying degree of sexual excitement, or may take the form of a 

 most elaborate display comparable to the nuptial antics of 

 some birds. The relation, however, only appears to last for 

 the period of pairing, or, at the most, for one breeding season, 

 and there is nothing that can be described as personal affection 

 between the two fish. The courting habits of the Httle Fighting- 

 fish {Betta) of Siam are worthy of special mention. The 

 brilliantly coloured male swims round and round his mate, 

 his beautiful fins extended to their utmost, his mouth wide 

 open, the gill membranes protruded and the bright-red gills 

 visible beneath. During these preliminary movements the 

 already vivid hues become even more intensified, and his body 

 and fins have been described as "resplendent with iridescent 



