We learn that the equator is a line around the wide waist of the world. Pleasure cruisers often make a great toâdo about crossing this line on the ocean. Any passenger who owns up to the fact that this is his first crossing may be put through ceremonies such as walking the plank and other merry goingsâon.
Ectoderm â Outer or External Layer â differentiates into the nervous system, epidermis, and the outer part of the integument system â forms the central nervous system, the lens of the eye, cranial and sensory, the ganglia and nerves, pigment cells, head connective tissues, the epidermis, hair, and mammary glands.
Germ Layers. by Kate MacCord Keywords: Germ layer theory, mesoderm, endoderm, ectoderm. A germ layer is a group of cells in an embryo that interact with each other as the embryo develops and contribute to the formation of all organs and tissues.All animals, except perhaps sponges, form two or three germ layers.The germ layers develop early in embryonic life, through the process of gastrulation.During gastrulation, a hollow cluster of cells called a blastula reorganizes into two primary germ layers: an inner layer, called endoderm, and an outer layer, called ectoderm. germ layer is a group of cells in an embryo that interact with each other as the embryo develops and contribute to the formation of all organs and tissues. All animals, except perhaps sponges, form two or three germ layers.