restriction. n. 1. something that restricts; a restrictive measure, law, etc. 2. the act of restricting or the state of being restricted. 3. (Logic) logic maths a condition that imposes a constraint on the possible values of a variable or on the domain of arguments of a function.
The primitive gut that forms during gastrulation in the developing embryo is known as the archenteron or the digestive tube.It develops into the digestive tract of an animal.ach is controlled by the dorsal blastopore, and primitive node (also known as Hensen's node), respectively. During Gastrulation, the Archenteron develops into the digestive tube, with the blastopore developing into either the mouth (Protostome) or the anus (Deuterostome).
Invertebrates. 1  Sponges are the most primitive of animal groups. 2  They live in water (usually saltwater), are sessile (do not move from place to place), and filter tiny organisms out of the water for food. 3  Coelenterates are also very primitive.lmost all animals fall into one of two groups. Adult vertebrates have a spinal column, or backbone, running the length of the body; invertebrates do not. Vertebrates are often larger and have more complex bodies than invertebrates.