In this article we will discuss about:- 1. Origin of Cyclostomes 2. General Characters of Cyclostomes 3. Classification 4. Representative Types 5. Affinities. Origin of Cyclostomes: The Cyclostomata (Gr., cyklos = circular + stoma = mouth) are the living agnathans, they are primitive in many respects, but specialised in others. They are a modified and degenerate offshoot of the primitive [...]
In this article we will discuss about the external features of lamprey with the help of suitable diagrams. Also learn about its habit and habitat. Shape and Size: The body of adult Petromyzon is elongated, cylindrical and eel-like. Petromyzon marinus (sea-lamprey) attains a length of a metre, Lampetra fluviatilis (Lampern or common freshwater lamprey) reaches a length of about 90 [...]
The pigeon, like other vertebrates, has receptors or sense organs for touch, smell, taste, sight and hearing which are stimulated by the environment. These sense organs are termed external receptors or exteroceptors. The pigeon possesses following exteroceptors: 1. Tactile Organs: These are poorly developed in birds due to feathery covering of the body. Tactile organs of pigeon remain confined to [...]