The following table, worked out by ffunder (1931), throws some light upon this question. 



Table 2. 



Species 



of 



Fish 



Eye 



Lateral Line 



Smell 



Taste 



Att. Cond. Cent. Att. Cond. Cent. Att. Cond. Cent. Barb. Lips. Mouth 



Carp 



Tench 



"Blei" 

 (Abramis brama) 



"Dobel" 



(Squalius cephalus) 



Trout 



liinnows 



Pike 



Perch 



Stickle-back 



(*) (*) 

 (*) (*) 



(*) 



(*) 



Att .; Attraction; Cond .; Conduction; Cont . ; Control 



Every trout breeder knov/s iiow greatly trout depend upon vision in their search for food. 

 Qri the other hand, it is interesting to note that in case of eye trouble, followed by total 

 blijidness, the olfactory sense will replace the sense of vision to a great extent, and will 

 enable the trout to search for food upon the bottom of the pond. 



Investigations by F. Schiemenz (192A) and Harter (1920, 1930) have revealed the fact 

 that fish distinguish very v/ell colors, size, differences in light and also shapes with 

 their eyes, and soan learn the characteristics of their preferred food along these lines. 



The di.qestive ornans— of which we cannot deal here — of carp and tenches differ funda- 

 mentally from those of trout. Hence, differences also exist in the respective processes of 

 digestion. 



The relatively long intestinal tract of carp, which has seven windings, is without a 

 stomach, hence, minus acid producing and pepsin producing gastric glands. The reaction 

 within the intestinal tract is about pK eq. 6.7 to 7.7 and the task of producing protein 

 digestion is chiefly performed by enzymes, developed in the pancreas. This is inqwrtant 

 to remember since pepsin performs a better task than trjTJsine, especially in the case of 

 proteins derived from chicken, blood, curd, sinews, glue and horn-like substances, etc. 



On the oth>;r hand, some authors maintain that trypsine reacts especially strong in fish. 

 This perhaps explains the practical experience that artificial food is badly digested by 

 carp-iike fish, if not 50 per cent, at least, of natural food is given at the same time. 

 It has been pointed out at all times that the intestinal ferments of eaten aquatics are of 

 great in^iortance — aside from vitamin contents — to the digestion of carp-like fish. 



16 



