embody] the horned DACE 171 



THE YOUNG CHUB 



The newly hatched fish (figure i) is very sraal] and so transparent 

 that it is seen with difficulty. If placed in a watchglass and viewed 

 with a hand lens against a background of black paper, something 

 of its form and external structure may be made out. 



When quiet the young chub is usually resting on its side or 

 else is attached to the side of the watchglass by means of an ad- 

 hesive substance secreted at the front of the head. This latter 

 is an important provision common among young fishes by means 

 of which they may suspend themselves above bottom on any 

 submerged object thereby preventing suffocation which might 

 otherwise occur from the deposition of sediment. ., . - . 



Fig. 1. Chub at hatching ; e, eye; ^, head; /, median 



tail fin; y, yolk sac. Length, 22 inches. 



Magnification 12.5 diameter. 



When moving the young chub swims rapidly in circles, spirals 

 or in very erratic manner all over the watchglass. It cannot 

 rise up in the water and remain there nor can it swim in a definite 

 direction in search of food, for it not only lacks internal control 

 of its movements but is without the necessary organs, such as 

 paired fins directly concerned in the execution of these movements. 

 Only a median vertical tail-fin is present and used for a forward 

 locomotion alone. Nature, again, has provided amply, for its 

 nourishment in the form of a yolk-sac full of richest nutriment. 

 Although this sac is heavy and interferes with the movements of 

 the fish, yet it provides that which is necessary for the fish to 

 develop and grow more like its progenitors. Coincident with the 

 disappearance of this sac, we find a development of the paired 

 fins which begin to function just before it is necessary for the fish 

 to seek its own food (figure 2). At this stage we find the young 

 fish rising slowly from the bottom, moving in a definite manner 

 in any direction and at short intervals snapping up both organic 

 and inorganic particles fioating in the water. 



