212 



MARKETAliLE HRITISH MARINE FISHES 



over the edge of the head. These fishes were very small, less 

 than an inch long, and Malm concluded that this was the way 

 in which the curious position of the eyes was reached. He was 

 able to prove that in the flounder when it began to develop in 



Fig. 10° 'l^'^'"' .|^\^^ 



Fig. 104 



Fisj. loi 



Fi". 10; 



Fig. 105 



Figs. 100-105. — The two sides of the head in three different stages in a left-sided 

 j'oung fiat-fish in which the right eye passes through the head region to reach the 

 left side {Rhonihoidichtliys). The two upper figures show an eye on eacli side of 

 the head, but the right eye is higher in position. In the middle figures the right 

 eye is beginning to appear on the left side through a slit above the left eye. In 

 the third figures the passage of the right eye is very nearly completed. (After 

 Steenstrup. ) 



the Qgg there w^as an eye on each side of the head. About the 

 same time, in the years between i860 and 1870, a naturalist in 

 Denmark obtained some small specimens of flat-fishes in which 

 the eye of the lower side was in various stages of migration 

 through the head, sinking in on one side and coming out again 



