Radiates (12th Rank)

These are animals:

• with a regenerating body
• without a head, eyes, articulated limbs
• with a mouth on the under surface, and a radiating arrangement in their internal and external parts.

These:

• occupy the 12th rank
• make up 1 of the 3 last classes of invertebrate animals

This class includes animals with a general shape and arrangement of parts and organs, both external and internal, which nature has not used in any animals of the previous classes.

The radiates have in their internal and external parts a radiating arrangement around a centre or an axis which makes up a special shape which nature has not, up to that point, ever used.

She began to sketch out such an arrangement only in the polyps, which, consequently, come after the radiates.

The radiates make up in the animal scale a compartment very different from that of the polyps, so that it is no longer possible to confuse the radiates with the polyps any more than it is to group the crustaceans with the insects or the reptiles among the fish.

Their organs appear destined for respiration (tubes or types of aquatic trachea).

They have special organs for reproduction, like types of ovaries in various shapes.

Nothing similar is found in the polyps.

Moreover, the intestinal canal of radiates is not generally a closed tube with only one opening, as in all the polyps. And the mouth, always low down or on the lower surface, manifests in these animals a special arrangement which is not at all the one which the polyps display in their general structure.

Although the radiates are truly curious and as yet little understood animals, what we know about their organic structure clearly indicates the rank to which I am assigning them. Like worms, the radiates are headless, eyeless, without articulated limbs, a system of circulation, and perhaps without nerves.

However, the radiates come necessarily after the worms. For the latter have nothing in the arrangement of their interior organs which tends to a radiating shape, and it is among them that the style of articulations begins.

If the radiates lack nerves, they are then without the faculty of feeling and are no more than merely irritable. This seems to be confirmed by observations made on living star fish in which the arms have been cut off without their showing any sign of pain.

In many radiates fibres are still distinct.

But can we call these fibres muscles, unless we are justified in stating that a muscle deprived of nerves is still capable of carrying out its functions?

Do we not have, in plants, the example of the potential possessed by cellular tissue of being reduced to fibres without our being able to consider these fibres muscles?

Every living body in which we make out fibres does not, it seems to me, have muscles just for this reason. And I think that where there are no more nerves, the muscular system no longer exists. There is reason to believe that in animals without nerves the fibres which we can still come across there possess, through their simple irritability, the faculty of producing movements which replace muscular movement, although with less energy.

In the radiates, not only does it appear that the muscular system no longer exists, but also that there is no more sexual reproduction. In fact, nothing gives evidence of that or even indicates that the small oviform bodies, whose mass make up what we call the ovaries of these animals, undergo fertilization (and are thus true eggs). This is all the more implausible when we find them equally in every individual. Thus, I consider these small oviform bodies to be internal gemmules already perfected, and their clumping together in special places is the method nature has prepared to arrive at sexual reproduction.

The radiates, confirm, in their turn, the general degradation in the organic structure of animals. For in this class of animals, we meet a new form and arrangement of parts and organs which are far distant from those of animals in the preceding classes. Moreover, they appear to lack feeling, muscular movement, and sexual reproduction. Among them, we see the intestinal canal cease to have two openings, the clusters of oviform corpuscles disappear, and the bodies become entirely gelatinous.

Observation

The very imperfect animals, like the polyps and the radiates, the centre of movement of the fluids no longer exists except in the alimentary canal.

There it commences to establish itself, and by the way of this canal the subtle ambient fluids mainly enter to stimulate movement in the containing fluids appropriate to these animals. What would plant life be, without external stimuli, and, by the same token, what would life be for the most imperfect animals without this cause, that is to say, without the heat and electricity of the environmental surroundings.

Undoubtedly, through a sequence of this sort employed by nature, first with a feeble energy in the polyps and later with greater developments in the radiates, the radiating form was acquired. For the subtle ambient fluids, by penetrating through the alimentary canal and expanding, must have, by means of a constantly renewed expulsion from the centre towards all the points on the circumference have given rise to this radiating shape in the parts.

This is the reason why, in the radiates, the intestinal canal, although still very imperfect (because very frequently it only has one single opening) is nevertheless complicated with numerous radiating vasculiform and often branching appendixes.

For the same reason in the soft radiates, like the jelly fish, and so on, we see a constant isochronous movement, a movement which very probably results from successive irregular movements in the masses of subtle fluids which penetrate into the interior of these animals and also the movements of these same fluids which escape after being spread throughout every part.

We should not say that the isochronous movements in the soft radiates are the consequences of their respiration.

For after the vertebrate animals, nature does not manifest in any other animal alternating and measured movements of inhaling and exhaling. Whatever the respiration of radiates may be, it is extremely slow and goes on without perceptible movements.