The relationship between metagenesis and polymorphism has raised the question—is metagenesis an outcome of polymorphism or has it lead to the emergence of polymorphism? A discussion on the existence of different grades of metagenesis in cnidarians will help us to find a logical answer. Gradations of Metagenesis: Four different forms of life-histories are seen in the cnidarians which exhibit a [...]
Learn about the comparison between Aurela and Urticina. Comparison # Aurelia: 1. Aurelia is elongated tube-like body with narrow proximal end differentiated into stalk for attachment. 2. Aurelia is about 1.5 cm in height. 3. Distal tentacle: 16 solid tentacles developed in regular order (4 per-radial, 4 inter-radial and 8 ad-radial tentacles). 4. Manubrium is present in Aurelia. 5. Mouth [...]
In this article we will discuss about the interrelationships between the different classes of phylum Cnidaria. Class Hydrozoa represents the most primitive forms amongst the Cnidarians. The lowest hydrozoan form is exhibited by Hydra and the hydrula stage of some Hydrozoa. The relationship between Hydrozoa and Scyphozoa is not very clear. In spite of this, it can be suggested that [...]