In the early decades of the twentieth century T.H. Morgan and his associates A.H. Sturtevant, H.J. Muller, C.B. Bridges and a few others at Columbia University, New York were actively engaged in studies on Chromosome Theory of Heredity with a very suitable material Drosophila. From their studies on mutants in Drosophila they could assign several genes to chromosomes. For their [...]
The following points highlight the two types of germinal layers of the animals. The types are: 1. Segmentation 2. Development. Germinal Layers: Type # 1. Segmentation: Segmentation is division or differentiation of the body into distinct portions called segments. It is of two types: metameric segmentation and pseudo-metamerism. I. Metameric Segmentation (True metamerism or True segmentation): It is a type [...]
The following points highlight the two types of eggs. The types are: 1. Eggs Based on Quantity of Yolk 2. Eggs Based on Distribution of Yolk in Cytoplasm. Type # 1. Eggs Based on Quantity of Yolk: 1. Microlecithal Eggs: They contain very small amount of yolk, e.g. eggs of Sea urchin, Herdmania, amphioxus. The eggs of man contain very [...]