170 ANIMAL ACTIVITIES, 
fin along the median ventral line is the aval or ventral 
fin. The fin at the end of the tail is the camdad fin, 
Sketch a fish with fins extended. Indicate the names 
of the fins. 
Of what use are the bones in the fins (finsrays)? 
Docs the fish swim by using: its fins, or its tail, or 
both ? 
The Head. What organs of sense do you find ? 
The cars are internal. 
Are the eyes movable?) Do they have lids? Plow 
docs the eye of the fish resemble the eye of man? ol 
the grasshopper? Flow dees it differ from these ? 
Do the nostrils open into the mouth? Use a tooth 
pick for a probe. Arc the nostrils of ase in breathing: ? 
Of what use are they ? 
Docs the mouth open vertically, or laterally 2? Where 
wre the teeth situated ? What is their shape? Whit 
about the shape and position of the tonpue ¢ 
Gills and Heart. What movements does the fish 
make while breathing: ? 
Kaise the gill-cover of the specimen on the bench. 
‘low many gills do you find? Tow many pill-cletts 
yy Spaces between the pills ? 
The bony supports of the gills are called AramAfal 
arches. Vhe soft delicate red branches from these 
arches are the gil-filaments. In these the blood is 
purified. What is the color of the blood of a fish? 
Can you see the branchial arches by lookinge inte the 
mouth of a fish ? 
Kemove the skin and muscular walls from that por- 
tion of the ventral cavity directly behind the galls, 
This exposes the heart. Can you cee the swellinges 
indicating the two cavities of the heart, the analy and 
the ventricle 2 The ventricle has the form of a tris 
angular pyramid, “Uhe auricle is thin-walled andl tiled 
with venous blood, hence it looks like a clot of blood 
attached to the ventricle. ‘The Jarge blood-vessel 
from the heart to the gills is the ventral aorta. [hs 
