Distribution of Animals Established by Linnaeus

Finally Linnaeus, a man of a superior genius and one of the greatest known naturalists, after having collected the facts and taught us to use great accuracy in the determination of characteristics for all the orders, gave us the following distribution for the animals/

He distributed them in 6 classes based on 3 stages or characteristics of their organic structure.

Distribution of Animals Established by Linnaeus

1. Mammals | A heart with two ventricles, red blood and warm
2. Birds

Except for the inversion which this distribution manifests, like all the others, the four first divisions which it presents are now definitely fixed and will always be accepted by zoologists insofar as their position in the general series.

The case is not the same with the last 2 divisions of the distribution under discussion.

They are poor and very badly arranged.

Since they include the greatest number of known animals and those with the most diverse characteristics, they should be more numerous.

It is therefore necessary to reformulate them and to substitute others for them.

Linnaeus and the naturalists who followed him, gave so little attention to the need to multiply the divisions among the animals with a cold serum in place of blood (the animals without vertebrae) and those in which the characteristics present such a great variety, that they distinguished these numerous animals in only two classes, as follows:

in insects and worms.

As a result, everything which was not considered an insect, or alternatively, all animals without vertebrae which did not have articulated members were, without exception, included in the class of worms.

They placed:

• the class insect after the fish
• the class worms after the insects

The worms therefore formed, according to this distribution of Linnaeus, the last class of the animal kingdom.

These 2 classes are still laid out following this order in all the editions of Systema naturae published after Linnaeus.

The essential problem of this distribution, so far as the natural order of animals is concerned, is evident.

Linnaeus’ class worms is a chaos in which things very different are found united.

His authority was so weighty among naturalists, that no one dared to change this monstrous class worms.

Intending to institute some useful reforms in this matter, I presented in my first course of study the following distribution for the animals without vertebrae, which I divided, not into two classes, but into five in the order given below:

Distribution of Animals Without Vertebrae as Laid Out in My First Course of Study

1. Mollusks
2. Insects
3. Worms
4. Echinoderms
5. Polyps

These classes were made up then of some of the orders which Bruguiere had presented in his distribution of worms, an arrangement I did not adopt, and from the class insects, such as Linnaeus had described it.

However, towards the middle of 1795, when the arrival of Cuvier in Paris directed the attention of zoologists to the organic structure of animals.

I saw, with much satisfaction, the decisive proofs which he provided for the preeminence which must be given to the mollusks over the insects, so far as concerns the rank which these animals must occupy in the general series, something which I had already carried out in my classes but which had not been viewed favorably on the part of naturalists of that capital city.

The change which I had made in this matter, from a sense of the inconvenience in Linnaeus’ distribution which people followed, Cuvier endorsed perfectly through his explanation of the most reliable facts, among which several, in truth, were already known, but which had not yet attracted our attention in Paris.

Profiting then from his illumination, since his arrival, has shed on all parts of zoology, and especially on the animals without backbones, which he called animals with white blood, I added successively new classes to my distribution.

I was the first to institute them. But, as we are going to see, the classes of mine which were adopted were only accepted slowly.

What interests authors is a matter of total indifference to science and also to those who study the subject. Nevertheless, there is a practical value in knowing the history of changes which the classification of animals has undergone in the past fifteen years. Here are those which I have effected.

To begin with, I changed the denomination of my class of echinoderms into that of Radiata, in order to unite in it the jelly fish and the genera which are related to them. This class, in spite of its utility and the necessity for it on account of the characteristics of these animals has not yet been adopted by the naturalists.

In my course for Year Seven (1799), I established the class crustaceans. At that time Cuvier in his Table of Animals, page 451, still included the crustaceans among the insects, and although this class is essentially distinct from the insects, nonetheless, the naturalists consented to adopt it only six or seven years afterwards.

The following year, that is to say, in my course for Year Eight (1800), I presented the arachnids as a special class, easy and necessary to distinguish. The nature of its characteristics were from that time on a certain indication of an organic structure peculiar to these animals, for it is impossible that an organic structure perfectly suitable to the insects, who all undergo metamorphoses, reproduce themselves only once in the course of their lives, and have only two antennae, two faceted eyes, and six articulated limbs, could give rise to animals which never undergo metamorphosis and which, in addition, present different characteristics which distinguish them from the insects. A part of this truth has since been confirmed by observation. However, this class arachnids has not yet been admitted in any work other than mine own.

Once Cuvier discovered the existence of arterial and venous vessels in different animals which people confused under the name worms with other animals very differently structured, I immediately used the implication of this new fact to perfect my classification. In my course for the Year Ten (1802), I established the class annelids, a class which I placed after mollusks and before crustaceans, something required by their acknowledged organic structure.

In giving a particular name to this new class, I was able to keep the ancient name worms for the animals which had always carried it and whose organic structure obliged me to distance them from annelids. Thus, I continued to place worms after insects and to distinguish them from radiata and polyps, with which people will never be authorized to unite them again.

My class annelids published in my course and in my Researches into Living Beings (p. 24) was around for several years without being accepted by naturalists. Nevertheless, for about the past two years, people are starting to recognize this class. But since people are of the opinion that they should change its name and to bring in the name worms for it, they do not know what to do with the creatures properly called worms, which do not have nerves, nor a system of circulation, and in this quandary, they are reuniting them with the class polyps, even though they are very different from them in their organic structure.