Classes of Animals Without Vertebrae

These examples of perfection first established in parts of a classification.

Later, they were destroyed by others.

Then they were reestablished by the necessity and the pressure of things in the natural sciences.

Linnaeus combined several plant genera which Tournefort had previously separated such as his general polygonum, mimosa, justicia, convallaria, etc.

Now, botanists are reestablishing the genera which Linnaeus had destroyed.

In 1807, I established among the animals without vertebrae a new 10th class, the infusorians because they are not part of the polyps.

This leads to 14 Classes.

10 Classes of Animals Without Vertebrae (Complex to Simple)

Mollusks Cirrhipeds Annelids Crustaceans Arachnids Insects Worms Radiata Polyps Infusorians

4 Classes of Vertebrate Animals

Mammals Birds Reptiles Fish

In the limits of the classes, there are some races that are half-way or intermediate between 2 classes.

Such is the present state of the general distribution of animals.

All the classes of the animal kingdom form necessarily a series of large groups according to the growing or declining complexity in their organic structure.

Should we go from simple to complex or from complex to simple?

Chapter 8 will answer this.

Nature marches in a certain direction.

A remarkable degradation is found in all organic structure if one moves from the most complex to the simplest animals.

This degradation is not nor can be finely demarcated.

Yet it exists in the main groups so evidently and consistently.

Even in the variations in the path, it depends on some general law which we should discover.