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 habit, habitat and life history of Obelia. Habit and Habitat of Obelia: Obelia is a typical representative of colonial hydrozoa (Fig. 12.14). It is exclusively marine. It exists in two principal forms, the polyp and the medusa. The polyp or hydroid form represents the asexual phase of its life-history and the medusoid [...]