SUMMARY. 
211 
Vertebrata, Class IV.— AMPHIBIANS (pp. 36-39). 
Characteristics : 
1. The fourth class of the Vertebrata in order of development. 
2. The covering generally consists of soft moist skin. 
3. The young are hatched from eggs , but undergo a later metamorphosis. 
4. The head is doubly -jointed with the backbone. 
5. The heart is two-chambered in the young; three-chambered in the 
adult. The blood is cold. 
6. The chest (thorax) and belly (abdomen) are not separated by a dia- 
phragm. 
7. Breathing is carried on by means of gills in early life, and by lungs 
at a later period. 
8. The thorax is bounded by ribs (generally). 
9. The limbs are never converted into fins, as in Fishes. 
10. There are teeth generally. 
Orders--— (See p. 234.) 
Vertebrata, Class V. — FISHES (pp. 39-46). 
Characteristics : 
1. The fifth and lowest class of the Vertebrata in order of development. 
2. The covering is of scales. 
3. The young are hatched from eggs. 
4. The head is singly -jointed to the backbone. 
5. The heart is two-chambered , and the blood cold. 
6. The chest (thorax) and belly (abdomen) are not separated by a dia- 
phragm. 
7. Breathing is effected by gills during the whole lifetime. 
8. The thorax is not bounded by the ribs. 
9. The limbs take the form of fins, but there are generally other fins as well. 
10. They have teeth. 
DIFFERENCES BETWEEN CLASSES IY. AND Y. 
Amphibians. 
1. Have lungs at adult stage. 
2. Limbs are not converted into 
fins. 
3. The heart is three -chambered 
(in the adult). 
4. They undergo metamorphosis. 
Fishes. 
1. Never have lungs. 
2. Fins, instead of limbs proper. 
3. The heart is two -chambered. 
4. They do not undergo metamor- 
phosis. 
Kinds. — For chief orders see p. 234. 
