FISHES. 



171 



About one hundred and forty sj^ecies are now known, from the streams and brack- 

 ish lagoons of the eastern United States, tropical and South America, Africa and Asia. 

 Few are found in Europe, and few in the north Pacific region, and none much north of 

 the latitude of Boston. The majority frequent brackish lagoons, lowland swamjjs, and 

 mouths of rivers, but the strictly fresh-water species often abound in the clear fountain- 

 heads of streams. Some African species live in hot sj^rings. 



The species are all of small size, some of them {Heterandria) being the smallest known 

 vertebrates. The largest species (Anableps, Fundulus) seldom reach the length of a 

 foot. In most species the sexes are dissimilar, and in several genera the anal fin of the 

 male fish is modified into an intromittent organ, whereby the ova are fertilized before 

 exclusion. Such sj)ecies are ovo-viviparous, the young being developed in a sort of 

 uterus, and being born at a comi^aratively advanced stage of growth. At birth, they 

 closely resemble the adult fish. Most of the viviparous species feed upon mud ; the 

 others upon insects and small oi'ganisms. The majority are surface fishes, swimming 

 about slowly, with their eyes partly out of the water. Others ( Cyprinodon, Fundulus) 

 are more active, and keep near the bottom, but always in very shallow waters. None 

 of the species have any economic value. All are very tenacious of life. 



Of the numerous genera, the following are some of the most noteworthy. The 

 genus Cyprinodon comprises numerous chubby little fishes of the shores of America 

 and southern Europe, provided with tricuspid incisor teeth. They are oviparous and 

 carnivorous. Similar to these, but 

 with a long dorsal fin and a general 

 resemblance to young sun-fishes, is 

 the genus Jordandla of the lakes 

 and everglades of Florida. Most 

 of the larger species belong to the 

 genus Ftmdulus, which is widely 

 distributed both in fresh waters 

 and in salt. The largest North 

 American species is Fundulus 

 majalis ; the most common, Fun- 

 dulus heteroclitus. 



Of the genera with modified 

 anal, and consequently ovo-vivipa- 

 rous, we may notice Gambusia. 

 One species of the genus ( Gambusia patruelis) abounds in all swamps and brooks of 

 the lowlands of the south, and brings forth its brood in early spring. The males are 

 smaller than the females and are much less numerous. 



Allied to Gambusia are Mollienesia, with large, banner-like dorsal fin, Pcecilia, 

 with smaller fins, Xiphophorus, with a sword-shaped lower lobe to the caudal, Goodea, 

 with tricuspid teeth, and Heterandria with small teeth in a single row. Heterandria 

 formosa, a pretty little fish of the southern lowlands, is said to be the smallest of 

 fishes, rarely exceeding half an inch in length. 



The most curious of the Cyin-inodontidse is the genus Anableps of the streams of 

 tropical America. These are surface-swimming fishes, like Gambusia and Zygonectes. 

 The prominent eye is divided by a horizontal partition into two parts, the upper 

 adapted for vision in the air, the lower in the water. These fishes reach a length of 

 more than a foot, being the largest of the Cyprinodontidee. 



Fig. 105. — Gambusia patruelis, top miunow, male and female. 



