THE AQUATIC VERTEBRATES 1047 



them attached to the ventral surface. Several African and South 

 American Cichlids carry the eggs and young in their mouths and 

 gill chambers. The so-called myth, that a given fish leads about 

 his brood and guards them in his mouth when danger approaches, 

 is not a myth for some of these species. 



The blind fishes of North America carry their eggs in their gill 

 chambers. In these fishes the oviduct has moved forward so that it 



FIG. 1542. Rainbow Darter, Etheostoma caeruleum Storer, $ . 



opens just behind the isthmus. The young are carried for a month 

 or two until they have reached a length of 10 mm. In a group of 

 Cyprinodonts reaching as far as Indiana, but increasing in diver- 

 sity of species and numbers of individuals southward, the eggs are 

 retained by the female until the yolk is absorbed by the growing 

 young fish, and sometimes for a much longer period. In the 



FIG. 1543. Rainbow Darter, Etheostoma caeruleum Storer, 9- Actual size, 50 mm. 



blind fishes of Cuba the young are about an inch in length at the 

 time of birth and in the California surf-perch they may be twice 

 as long. 



Secondary Sexual Characters. Such features consist in size, 

 disposition, color, or structure. Large differences in all of these 

 are found in the killifishes. In some of these species the male 

 is minute and provided with an anal fin modified into a lance- 



