The 6 Stages
Table of Contents
I have divided into 6 very distinct stages all the styles of organic structure in the animal ladder.
Of these 6 stages, the 4 first ones include the animals without vertebrae.
This will make it easier to follow the march of nature in her production of animals.
This is the way in which for several years in my lessons at the Museum I set out the invertebrates, always proceeding from the most simple towards the most complex.
| Stage | Description |
|---|---|
| 1 | No nerves, no vessels, no special internal organs other than for digestion |
| 2 | No knotty (ganglionic) longitudinal chord; no vessels for circulation; few interior organs other than those for digestion |
| 3 | Nerves ending in a knotty (ganglionic) longitudinal chord; respiration by aerated gills; circulation is absent or imperfect |
| 4 | Nerves ending either in a brain or in a longitudinal ganglionic chord; respiration by gills; arteries and veins for circulation |
| 5 | Nerves ending at a brain which does not fill the skull cavity; heart with one ventricle; cold blood |
| 6 | Nerves ending in a brain which fills the cranial cavity; heart with two ventricles; warm blood |
Here is a table of the 14 classes dividing the animal kingdom.
Table of the Distribution and Classification of Animals
Invertebrates
| Stage | Class | Name |
|---|---|---|
| 1 | 1 | Infusorians |
| 1 | 2 | Polyps |
| 2 | 3 | Radiates |
| 2 | 4 | Worms |
| 3 | 5 | Insects |
| 3 | 6 | Arachnids |
| 4 | 7 | Crustaceans |
| 4 | 8 | Annelids |
| 4 | 9 | Cirripeds |
| 4 | 10 | Mollusks |
Vertebrates
| Stage | Class | Name |
|---|---|---|
| 5 | 11 | Fish |
| 5 | 12 | Reptiles |
| 5 | 13 | Birds |
| 6 | 14 | Mammals |
Such is the table of the 14 classes for the known animals.
- It is arranged following the order which matches the order of nature.
We will always be forced to conform to this arrangement even if we refuse to adopt the lines of separation which form them.
This arrangement is based on the analysis of the organic structure of living bodies.
Of first importance is:
- the affinities which exist among the objects in each division
- the rank of each of these groups
People will never find solid reasons for changing this distribution in its entirety.
But we will be able to make changes in:
- the details
- the divisions subordinate to the classes
This is because the affinities between objects comprising the sub-divisions are more difficult to determine and assume a more arbitrary character.
This arrangement and distribution of animals conform to the very order of nature.
I am going to reveal the general series of known animals, divided into its principal divisions, proceeding from the simplest towards the most complex, in accordance with the reasons indicated above.
This will make us recognize the rank, in the general series, of animals.
However, I will give here only a simple list of genera and only of the principal divisions; but this list will be sufficient to demonstrate the extent of the general series, its arrangement conforming the most with the order of nature, and the indispensable placement of classes, orders, and thus, perhaps, of families and genera. We understand well that it is in the good works of zoology which we possess that we must study the details of all the objects mentioned in this list, because I have not taken that into consideration in this work.