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TEXTBOOK OF ZOOLOGY 



the spinal cord. Each has a dorsal raraus, or branch, and a ventral 

 one extending out to certain parts of the body in the region. 



The sense of taste is highly developed and is centered in the numer- 

 ous and well-developed taste huds which are distributed on the inside 

 and outside of the lips, in the lining of the first three gill slits, on the 

 barbels, and in gTOups over the external surface of the body, even to 

 the tail. The eyes are small and without lids but have fair power of 

 vision as this sense goes in fish. The focal distance is between twelve 

 and eighteen inches, and is better for detecting motion than for 

 recognizing objects. The fish does not have a sense of hearing; 



Fig. 258. — Eggs of trout with well-developed embryos, and recently hatched 

 fry. A, eggs with embryos; B, fry. (Courtesy of General Biological Supply 

 House.) 



the ear structures serve in the sense of equilibrium. Ameiurus, perch, 

 and other fish have a well-developed pressure and water-vibration 

 sense centered in the lateral line system. The sense of touch is dis- 

 tributed over the epidermis but is particularly keen in the lips and 

 barbels. 



Reproduction and the Life History 



The bullhead, perch, sunfish and many other common fish build 

 nests of one sort or another, lay the eggs in the nest, and guard the 

 nest until the eggs hatch. The details of the reproduction and 

 breeding are not so well known in Ameiurus natalis as they are in 



