332 FISHES 



whose name means literally toothed carps, are confined to fresh 

 or brackish waters. The other four families are all members of 

 the most modern or specialised sub-order of spiny-finned fishes 

 (Acanthopterygii), and with the exception of the Comephoridae 

 are all marine. In the Californian surf-perches (Embiotocidae) 

 the physiological peculiarity is common to the whole family, but 

 in Comephoridae, Scorpaenidae, and Blenniidae it is confined to a 

 few species in each family. It is difficult therefore to attribute 

 the viviparous habit to the same conditions of life in all cases, 

 it appears to be in a sense accidental, although it has doubtless 

 arisen from an intensification of the sexual instinct of the male 

 which led him to an increasingly definite psychological interest 

 in the spawning of the female. In many fishes, as we have 

 seen, the males show a very distinct interest in the process of 

 fecundation and a strong association between their perceptions 

 of the female and of the eggs, and their own sexual excitement. 

 The nervous connection in such cases is no longer merely be- 

 tween the enlarged and mature sexual organs and the act of 

 expulsion of the contents of the latter, still less is there a merely 

 automatic escape of the milt, but the discharge is the response 

 to stimulation of the brain by the higher sense-organs. Such 

 stimulation and psychological excitement has led the male 

 gradually to anticipate the discharge of the eggs by the female 

 until the milt was actually introduced into the female aperture. 

 Once internal fertilisation has taken place, the explanation of 

 internal development offers little difficulty. 



It seems evident that such a development of the sexual in- 

 stinct could only occur in fishes of comparatively sedentary 

 habits, and under favourable conditions of life, in which food 

 was abundant and the persecution of enemies not very severe. 

 The Cyprinodonts are small fishes of which the largest do not 

 exceed a foot in length, and occur chiefly in the rivers and fresh 

 waters of the American continent, in the southern parts of 

 North America, in Central America, and in South America as 

 far south as La Plata. A few species are known from tropical 

 and subtropical regions of the Old World, namely Africa, India, 

 Arabia, and the East Indies. They are represented in the 

 more southern islands of Japan, and also in southern Europe, 

 namely in Spain, Italy and the Balkan peninsula. The Em- 

 biotocidae or surf-perches are confined to the north Pacific and 



