Class 3: Radiates
Table of Contents
Stage 2
No longitudinal ganglionic chord, no vessels for circulation; a few special internal organs (either tubes or pores taking in water or species of ovaries) other than those for digestion.
Class 3: Radiates
These are subgemmiparous animals, free or wandering:
- with regenerating bodies, a radiating arrangement of parts, both internal and external
- compound organ of digestion; lower mouth, simple or multiple. No head, no eyes, no articulated limbs; a few internal organs other than those for digestion.
Observations
These have a radiating arrangement of the parts, both interior and exterior.
These are no long animals with an elongated body, an upper terminal mouth, usually established in a polypary with a great number of them living together, each participating in a communal life.
These are animals with a more complex organic structure than in the polyps, simple, always free, with a design which is unique to them, and generally orienting themselves in an inverted position.
Almost all the radiata have tubes drawing in water which appear to be aquatic trachaea. And in a great number we find special bodies which look like ovaries.
Doctor Spix, a Bavarian physician, has discovered a nervous system in star fishes and sea anemones.
He says that in the red star-fish:
- under a membrane made up of tendons (like a tent) there is suspended on the stomach a reticular structure made up of whitish nodules and threads
- at the origin of each ray, 2 nodules or ganglia which communicate with each other by a thread and from which other threads leave and go to parts close by;
- among others there are two very long threads which run through the full length of the ray and supply the tentacles.
We see in each ray 2 nodules, a small extension of the stomach (coecum), two hepatic lobes, two ovaries and trachaeal canals.
In the sea-anemones, he observed at the base of these animals, below the stomach, a few pairs of nodules.
These are arranged around a centre, which communicate with each other by cylindrical threads and which send out other threads to the upper parts. Moreover, he saw there four ovaries surrounding the stomach, from the base of which canals leave which, after joining up, open into a lower point of the alimentary canal.
It is astonishing that such a complex organic apparatus has escaped the attention of all those who have examined the organic structure of these animals.
If Doctor Spix was not imagining things in in what he believed he saw and if he was not wrong in attributing to these organisms a nature and functions different from what is appropriate to them (something which has happened to so many botanists who believed they saw male and female organs in almost all the cryptogram plants), then the consequences are as follows:
(1) It is not in the insects that we must establish the commencement of a nervous system;
(2) This system must be considered as rudimentary in the insects, radiates, and even in the sea-anemone, the last genre of polyps;
(3) This is not a reason why all polyps should possess the rudiments of this system, in the same way that it does not follow that all reptiles are equipped with bills just because some have them.
(4) Finally, the nervous system is no less a special organ, not shared by all living bodies. For not only is it irrelevant in plants but it it is not even present in all the animals.
It is impossible that the infusorians are furnished with a nervous system and assuredly polyps in general are not capable of having one. Thus, we would look for it in vain in the hydras, which nonetheless belong to the last order of polyps, the one closest to the radiates, since it includes the sea anemones.
Thus, whatever the basis for the facts cited above, the points which I present in this work on the successive formation of the different special organs remain valid no matter at what point in the animal scale each of these organs originates. And it is always the case that the abilities which the organs provide for the animal do not begin to operate until the organ which provides them come into existence.
Radiate Orders
- Soft Radiates – Gelatinous body; soft skin, transparent, lacking articulated spines; no anus.
- Echinoderm Radiates – Opaque skin, crustaceous or coriaceous, furnished with retractable tubercules or articulates spines on tubercules, and pierced with holes in a series.
- 2a: Stellerides. Skin not irritable, but mobile; no anus
- 2b: Echinoids. Skin not irritable, not mobile; an anus
- 2c: Fistulides. Elongated body, an irritable and mobile skin; an anus
Table of Radiates
| Order | Members |
|---|---|
| 1 | Stephanomia Lucernaria Physsophora Physalia Velella Porpita Pyrosoma Beroe Aequorea Rhizostoma Medusa |
| 2a | Ophiura Asteria |
| 2b | Clypeaster Cassidites Spatangus Ananchytes Galerites Nucleoites Sea urchin |
| 2c | Holothuria Sipunculus |
Remarks
The sipunculus are animals very close to worms. However their known affinities with the holothuria have led them to be placed among the radiates, with which they no longer share characteristics. Consequently, they must come at the end.
In general, in a really natural distribution, the first and the last genera of classes are those in which the classical characteristics are less pronounced. Because they come at the limits of the class and the lines of separation are artificial, these genera must display to a lesser extent than the others the characteristics of their class.