3033. All animals which breathe by the anus, do so properly through the navel; animals of this kind are fundamentally umbilical animals.
Parallelism of the Fœtus with the Animal Classes.
3034. During its development the animal passes through all stages of the animal kingdom. The fœtus is a representation of all animal classes in time.
3035. At first it is a simple vesicle, stomach, or vitellus, as in the Infusoria.
3036. Then the vesicle is doubled through the albumen and shell, and obtains an intestine, as in the Corals.
3037. It obtains a vascular system in the vitelline vessels, or absorbents, like as in the Acalephæ.
3038. With the blood-system, liver, and ovarium, the embryo enters the class of bivalved Mollusca.
3039. With the muscular heart, the testicle, and the penis, into the class of Snails.
3040. With the venous and arteriose hearts, and the urinary apparatus, into the class of Cephalopods or Cuttle-fish.
3041. With the absorption of the integument, into the class of Worms.