154 



ZOOLOGY. 



The mnd-fisl-i of Western and Southern waters {Amia 

 calva) is a connecting link between tlie Ganoids and com- 

 mon or bony fishes. It bears a general resemblance to and 

 is about the size of a bass. Its tail is less " heterocercal " 

 than that of the garpike, and thus it comes nearer to the 

 bony fishes. 



Sub-Class III. — Teleostei (Bony Fishes, Perch, Cod, etc.) 



These are our common fishes, of which there are nearly 

 ten thousand species. The bones are small and exceedingly 

 numerous, a number of small bones forming the skull and 



Fig, 19B. — Anatomy of the Oiinner, male. L, lateral line; Hi, heart; Ps, pseiido- 

 branchia; Sp. spleen; S. air-bladder: Ki.Ki', kidney; bl, bladder: T, testis; 

 -4, aorta; B, brain; In, intestine: Li, liver; G, gills. Dra^vn bj C. S. Minot. 



supporting the fins, so tliat we may in a single fish count 

 upAvards of five hundred separate bones. In these fishes 

 there ai'e four gills on each side, the single gill-o]ieuing 

 being covered with a lid or operculum composed of four 

 thin bones. 



We would advise the student to dissect a percli, smelt, or any fisli, 

 with the aid of tlie following description of tlie anatomy of tlie sea- 

 perch, which closely rcaemliles tlie fresh-w.ater perch. With a pair 

 of forceps, sharp scissors and l^nife tlie student, by the exercise of 

 care, may make a very fair dissection. 



To dissect a perch the side-wdl of the mouth must tie removed, 

 then the gill-covcr; study the arrangement of the gills. Next make 



