In this article we will discuss about the historical resume and classification of jawless vertebrates. Historical Resume: L. Agassiz (1857) placed the agnaths under the class Myzontes and proposed the following scheme for the lampreys and hagfishes: Class I. Myzontes. Order 1. Myxinides and Order 2. Cyclostomi. E. S. Goodrich (1909) gave the following classification in his book "Cyclostomes and [...]
In this article we will discuss about Hagfish:- 1. Introduction to Hagfish 2. Habit and Habitat of Hagfish 3. External Structures 4. Digestive System 5. Respiratory System 6. Circulatory System 7. Nervous System 8. Excretory System 9. Reproductive System 10. Development 11. Affinities and Systematic Position. Contents: Introduction to Hagfish Habit and Habitat of Hagfish External Structures of Hagfish Digestive [...]
The swim-bladder in fishes and the lungs of tetrapods are closely similar in structure and development. Both these structures are intimately associated with the gut. The lungs of higher vertebrates arise exactly the same way as that of the swim-bladder in fishes. Both develop as outgrowths from the gullet and the glottis occupies exactly the same position. But the exact [...]