86 



HIGH SCHOOL ZOOLOGY. 



7. In regard to tho nervous sys- 

 tem of tlio Menobrancli, the most 

 notable difTerence from the catfish 

 will be found in the bi-ain (Fig. 63). 

 Here the olfactory lobes are vmited 

 with the larger and thicker-walled 

 cerebral hemispheres ; the inferior 

 lobes are not present, the oi^tic lobes 

 not so distinctly divided into right 

 and left halves, the cerebellum 

 quite rudimentary, and the medulla 

 oblongata destitute of those swell- 

 ings present in the catfish. 



8. The teeth in the Menobranch 

 are not only less numerous, but 

 they are confined to smaller sur- 

 faces within the mouth. There are 

 two rows in the upper jaw, of which 

 the posterior (on the vomer and 

 pterygoids) is tho longer, while the 



mandible has only a single row fitting in between the two of the 

 upper jaw. Unlike the fish there is a fleshy tongue free in 

 front and at the sides, and the tubercles on the concave surfaces 

 of the gill-arches are not so prominent as in the catfish. The 

 intestine hardly departs from the tubular form, the liver is 

 more elongated, and the jjancreas quite independent and much 

 subdivided. 



It is interesting to compare the lungs with the air-bladder of 

 fishes. The glottis is supported by two slips of cartilage which 

 occupy nearly the position of the fourth branchial arches; it 

 opens into a common chamber whence the thin-walled lungs 

 project back wai-d and two short blind sacs forward ; the latter 

 remind one of the similar points which are present in the air- 

 bladder of Amia. 



a i> 



Fig. 63.— Brain of Menobranch. 



A. From above. B. From below. 



Rh. Olfactory lobes; Pr. Cerebi'.al 

 hemispheres ; Thai. Thalamic region ; 

 Mes. Optic lobes ; cb. cerebellum ; h. 

 hypoi>hysis; Met. Medulla oblongata ; 

 2nd, rjth, 8th, 9th. Cranial nerves. 



