HIGH SCHOOL ZOOLOGY. 



8^ 



9. A comparison is more easily effected 

 between the heart and great vessels of the 

 Menobranch, and those of Amia and Lei)i- 

 dosteus or one of the Dipnoi, than those of 

 the catfish, because the ventricle has a 

 muscular cone in these forms which is ab- 

 sent in the catfish. From this the arterial 

 trunk comes off in front (Fig. 64) and di- 

 vides into two right and left branches, 

 which afterwards subdivide to form the 

 three afferent branchial arteries for the 

 three gills. The blood which is aerated 

 in the foremost and largest gill is partl}^ 



Fig. 64.— Diaprram of Heart 

 and Great W-ssclsof riylit 



side of Muuut) ranch. 

 Co. Arterial cone ; v. ven- 



triiie; a. aiuioie; i, ii.iii, uf- Sent to the head, but partly joins that 



ferent branchial arteries; G', r. •, ^ 



G-, G', tiietiiroe gills; ce,ci, ii-oni the efferent arteries of the second 



external 5t internal carotids; i i • i -n 



Pa. Pulmonary artery; o. and third giUs, SO as to form the dorsal 



branch to resophagu.s and , „ c J.^ i ^ ^ £■ i_i i 



stoinach; L. luug ; i>. dorsal aorta, feome ot the blood trom the second 



and third aortic arches reaches the lung 

 (only, however, in a partially aerated condition) through the 

 pulmonary artery, a modified fourth arch ; its aeration is com- 

 pleted in the lung, whence through a separate vessel, the 

 pulmonary vein, it reaches a special compartment of the 

 atrium, not quite separated off from the rest, but partly so by 

 an imperfect partition. In higher Amphibia this j)artition is 

 pei'fect, so that the blood within it is not mixed in the ventricle 

 with the returning venous stream, until some of it has been 

 already sent on to the head through the modified first arches 

 (carotid arteries). 



10. The kidneys are narrow ribl)on-like structures which 

 extend through the greater part of the length of the body 

 cavity. It is sujjposed that the Mcnobranchs spawn in spring, 

 and that they lay eggs nearly of the size of a pea, but further 

 information is desirable as to their haljits in this respect. 



