A MANUAL OF ZOOLOGY 45 



skill pores about the head of this fish? Make a drawing 

 of the lateral surface .of this' animal locating- the different 

 external features. . ' 



THE VISCERA— Cut away carefully one side &f the 

 body wall' from a short distance in front of the anal open- 

 ing to the pectoral fins and from the ventral line as far 

 dorsally as -you -can without injuring the viscera especially 

 the alT bladder^ ''Note the perftoneum. 



In the fore part of the body cavity lying mainly in 

 the left side is the liver. -How many lobes has it? Is. it 

 larger in siS;e compared to the bulk of the body • than it 

 is- in the dog-fish? Demonstrate the "gall bladder and the 

 hepatic veins passing forward from the liver. .Demonstrate 

 the oesopfragus and" the stomach by. passing a probe down 

 the throat. From the ahtertor part of the stomach find the 

 opening of the intestine. This form of stomach is called 

 Goecal. -Abo-ut' a half inch from the anterior «nd of the 

 intestine find projections from it, the- pyloric coeca. How 

 many of these are there? Cut off the end of one of the 

 coeca. Where does it lead*? What is its use? Is the 

 intestine convoluted?- Trace it to the anal ttpening. If the 

 stomach of the dog-fish is -of the more primitive type 

 from which the'T^leostian type is -a de-yelopmeht, how may 

 the opening of the intestine from the- anterior end be ac- 

 counted for? Do you find a 'pancreas?. (See Shipley and Mc- 

 ■BHde, page 381). Observe that the -viscera are held inplace 

 ,by a thin membrane,'- the mesentery. Notice how the 

 blood vessels are contained in it. Find a reddish body 

 near the intestine. This, is the spleen.- Dorsal to the 

 intestine in the female find a long granular yellowish body, 

 the bvary; This may be very large at certain times of 

 the year, when the -eggs are ripe. Trace the- oviduct. 

 Does it open into a cloaca? Does this reproductive appa- 

 ratus indicate -an advance in 'the scale above -the ^og-fish? 

 Why? If the fish is a male notice the two white bodies, 

 the testes. Trace the vas deferens. Find a urmary bladder 

 posterior to the reproductive organ's. 'Where is its external 

 opening? 'Ifi 'the dorsal part of the' body cairity find the 

 •air bladder. Whafis its use? Trace "carefully its anterior 

 end to see if It has a communication with the alimentary 

 panai Onen the oesoDhagus. stomach. and the intestines. 



