46 A MANUAL OF ZOOLOGY 



and note the differences in the character of the mucous 

 membrane lining them. Find the pyloric valve. Do the 

 pyloric coeca open into the intestines? In front of the 

 liver find a false diaphragm. Remove this and observe the 

 heart. The part most ventral and posterior is the ventri- 

 cle. The part above the ventricle is the auricle. Dorsal 

 to the aorta is a large thin-walled sinus venosus. Anter- 

 ior to the ventricle find the bulbus arteriosus. Is this 

 composed of different material from the ventricle? Trace 

 the ventral aorta leading from this forward until it divides 

 into two branches one going to each branchial aipparatus. 

 Observe along the dorsal part of the body cavity under 

 the peritoneum, the dorsal aorta. How many branches 

 does it give off to the viscera? Can you find the long 

 kidney on each side of the spinal column? Where do the 

 ureters leading frOm them go? 



Separate the lower jaws by a cut along the medial 

 line. Turn the sides back and notice how the gill rakers 

 fit into each other. Is the anterior row of gill rakers 

 different from the others? How? Observe where the gill 

 arches meet dorsally a large flat prominence constituting 

 the dorsal part of the pharynx. This is covered with 

 numerous fine teeth. Opposing these on the ventral side 

 is a smaller patch of teeth. These are called the superior 

 and the inferior pharyngeal teeth. Do the gill arches have 

 joints? The bones supporting these are the pharyngeal 

 bones. Carefully pick away the flesh from' the inside of 

 the pectoral and the pelvic arches so as to expose the 

 bones constituting the'se arches. The largest bone of the 

 pectoral aTch is the clavicle. It projects a little above the 

 base of the pectoral fin. Above this is the supra-clavicle. 

 The f>ost-temporal connects this latter with the' skull. The 

 bones connected with the venti'al fins ' may be considered 

 as the pelvis; Observe that they are directly connected 

 with the pectoral arch. How does this compare with the 

 dog-fish? With the higher forms? What would this indi-' 

 cate &6 to the place of the Teleoatomi In the evolutionary- 

 scale? Make a drawing of these bones together and one- 

 to i^ho^r the m'ethod of articulation ■ between the flhs and 

 these bones: Is this joint different from thit of the higher 

 forms'?- 



