DEGRADATION OF ORGANISATION «7 



When we reach this class we find animals with a general shape 

 and arrangement of the parts and organs, both internal and external, 

 that nature has not employed in any of the animals of the anterior 

 classes. 



The radiarians indeed conspicuously exhibit in their internal and 

 external parts that radiating arrangement around a centre or axis, 

 which constitutes a special shape not hitherto used by nature. Its 

 rudiments are found in the polyps, which accordingly come next. 



Nevertheless, the radiarians form a stage in the animal scale quite 

 distinct from the polyps ; so that we can no more confuse radiarians 

 with polyps than we can class crustaceans with insects or reptiles 

 with fishes. Among the radiarians indeed, not only do we find again 

 organs apparently intended for respiriation (tubes or kinds of water- 

 bearing tracheae), but we discover in addition special organs for 

 reproduction, such as kinds of ovaries of various shapes to which 

 there is nothing analogous in the polyps. Moreover, the intestinal 

 canal of the radiarians is not generally a cul-de-sac with a single 

 opening as in all the polyps ; their mouth is always on the inferior 

 surface and displays a special arrangement which is quite different 

 from that commonly found in polyps. 



Although the radiarians are very remarkable animals, and as yet 

 little known, what we do know of their organisation plainly points to 

 the rank which I am assigning to them. Like the worms, radiarians 

 have no head, eyes, jointed legs, circulatory system or perhaps nerves. 

 Yet the radiarians necessarily come next to the worms, for the latter 

 have nothing in the arrangement of their internal organs that suggests 

 a radiating shape, and it is among them that the system of articulations 

 begins. 



If the radiarians are destitute of nerves, they cannot have the faculty 

 of feeling, but are simply irritable ; this fact seems to be confirmed 

 by observations made on living star-fishes, whose arms have been cut 

 off without their showing any sign of pain. 



In many radiarians fibres may still be distinguished ; but can we 

 call these fibres muscles ? Not unless we are justified in saying 

 that a muscle can function without nerves. Do not plants show us 

 that cellular tissue may be reduced to fibres ? Yet we cannot possibly 

 regard these fibres as muscular. In my opinion it does not follow 

 that because a living being has distinguishable fibres, it must therefore 

 have muscles ; I hold that where there are no nerves, there is no 

 muscular system. There is reason to believe that in animals without 

 nerves the fibres which are still to be found possess the faculty by mere 

 irritability of producing movements which replace those of the muscles, 

 although less energetically. 



