Scientific Lectures. 925 



liatclied from the escg, tlie llonnder swims as otlier fishes swim, with 

 the back upr)ennost. Soon, however, the eye ui)on one side <.)f the 

 liead sh:>wly changes its position, and actually passes tlu-ough tlie 

 skull and conies out by the side of the otiier eye. The iiounder 

 then rests upon one side \vhic!i is white, or lighter in eoloi- than that 

 side which is turned toward the liglit. Among the batrachians the 

 limbs are modified to accord with their respective habits. In some 

 the mei-est rndiments are present. In the water newts the tail is 

 long and has a membraiieons fin rnnning along its up])er and lower 

 edge, and the tail is swung back and forth, as in the iishes. In 

 others, the hind legs are enoi'mously developed, the toes being webbed, 

 and are used for swimming and jumping. 



Snakes. 



Among the reptiles we have some singular modifications in their 

 h»coniotive apparatus, thus in the snakes we have a long cylindrical 

 body with the fore and hind limbs absent (except the rudiments of 

 hind legs in tlie boa), and yet, despite this deprivation, the snake 

 can move rapidly over the ground, can swim gracefully, can leap in 

 the air and climb trees, and, in short, can perform almost every mode 

 of locomotion except flying. We shall find upon examination that 

 eacii pair of ribs is connected with one of the ventral scales, the face 

 edge of which projects backward. These scales lap one over the 

 other, and the ribs, in swinging back and forth, also move the scales 

 whose sharp edges catch in the ground, and thus the body is impelled 

 forward. It will be remembered that a snake moves with ditiicultj 

 on a smooth surface, it is because the scales have no projections upon 

 which to catch. 



Among the turtles, while many are adapted to crawl upon the 

 land and have proper fore and hind legs, among the sea turtles, these 

 legs are changed to fins, and in one species, found rarely on (jur coast 

 (Piiargis Coriacea), the lecturer had made drawings of one whose 

 forward fins measured eleven feet from tij) to tip. 



In the birds we have various modifications of the wings and legs^ 

 suited to their different habits. The birds as a class, form the most 

 distinct groups in the animal kingdom. Xo one ever mistook a bird ; 

 while naturalists at one time regarded the whale as a fish, and corals 

 as plants, and barnacles as niollusks. No one has ever mistaken a 

 bird fur any other animal. I'iie characters of any one bird stand for 

 the whole class, they are all warm blooded, all breathe air, all are 



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