A MANUAL OF ZOOLOGY 37 



How many paired fins has the fish? How many unpaired? 

 Have the paired fins any relation to the limbs in the higher 

 forms? By worlcing the- anterior pair of paired fins, see 

 if you can determine something of the mode of connection 

 with the body. By pressing on the sltin ventrally and dor- 

 sally see if you can determine the presence of the 

 pectoral arch. In the same way try to determine the pelvic 

 arch in connection with the hind pair of ventral fins. Im- 

 mediately posterior to this latter pair in the angle formed 

 by their approach to the body the anal or cloacal opening 

 is found. If the fish is a male you will observe that the 

 inner part of each of these fins is specialized to form a 

 pair of sexual organs. Note the opening of the sperm duct, 

 Where is it found? The cloacal or tail fin is heterocercal. 

 (See Kingsley, page 229). On each side of the fish ex- 

 tending from near the spiracle, to the tail note the lateral 

 line. (See Weidersheim and Parker, page 191 and Weysse, 

 page 275). By pressing on the. skin of the fish taken 

 from the preserving fluid one may demonstrate the pores 

 of, the skin. They are especially' noticeable on the, head 

 near. the ^piracies. Examine the skin witb the hand lens. 

 It seems to be coy^red with fine teeth. Whfch direction 

 do they slant? Look up the word "shagreen". These 

 scales are of the placoid form. ' (See Kingsley, page 228). 

 Make a drawing of the external appearance. Make aT draw- 

 ing of the musculature on the side after the skin has been 

 removed. 



DIGESTIVE SYSTEM — Open the abdominal and the 

 thoracic cavities by a median cut extending from a short 

 distance in front of the anal opening to a point opposite 

 the posterior corner of the mouth. The body is lined with 

 a silvery membrane, the peritoneum. In the abdominal 

 cavity note the large bi-lobed liver. Between the lobes 

 of the Uver note the stomach connected by a short gullet 

 or oesophagus to the back part of buccal cavity or pharynx. 

 By pushing a scalpel handle or other blunt instrument 

 down the oesophagus demonstrate the connection with 

 the stomach. The stomach is V-shaped, the large anterior 

 end being known as the cardiac and the posterior end as 

 the pyloric stomach. Attached to the posterior end of the 

 cardiac stomach and extending around the angle of the V 



