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the Echinodeniis as original cormi or complexes of vermicular individuals, it is clear that 

 those forms must be the oldest or least changed, in which this cormus exhibits the least 

 degree of centralisation, and in which therefore the component individuals (persons) evidently 

 shew their original selfsufficiency as such. This is precisely the case with the star-fishes, 

 the rays or arms of which give, each for itself, a complete image of the whole organisation. 

 Among the star-fishes again, it is the genus Brisinga which in this respect most distin- 

 guishes itself; for which reason we must thus consider this form as the oldest or most 

 original of all the Echinoderms. To prevent misunderstanding, it must be expressly remar- 

 ked that this refers chiefly to the general combination of the body, not to the organisation 

 in its details. In this respect the Brisinga is in exact conformity, as has been shewn, with 

 the star-fishes now living; and it cannot fairly be assumed that these have been able to 

 preserve unchanged the self-same organisation of the ancient worm-like creatures from which 

 the whole tribe of Echinoderms proceeds. 



In the genealogical development of the tribe of Echinoderms, which may be sup- 

 posed to have progressed uninterruptedly in the immense periods during which the animals 

 hereto belonging have existed upon the earth, there appears chiefly to be manifested a 

 tendency towards greater and greater centralisation of the originally independent individuals 

 composing the cormus. The Echinoderms in which this has been in the highest degree 

 successful are undoubtedly the Holofhurians; and these must therefore be considered as the 

 newest, most divergently developed and most altered Echinoderms; this conclusion is also 

 corroborated by Paleontology; as we do not find any traces of these animals until the Jura 

 period; while all the other groups of Echinoderms are referred to far earlier times. Between 

 the 2 extreme points, the Asterise and Holothurife, there are a great number of in some 

 cases widely divergent series of developments, all of which may however be naturally refer- 

 red to the Asteria; as the proper fundamental forms. In examining the various groups of 

 Echinoderms, we shall find that the said tendency in the cormus, after this is centralised as 

 an independent physiological individual, takes 2 courses, both leading to the same end, 

 although in rather different manners; both are already partially indicated in the group of 

 Asteroidea, but only come to their full manifestation, on the one side in the Echinoids and 

 Holofhurians, and on the other side in the Ophiurans and Crinoids. 



One course consists in more or less extensive concrescence of the individuals (the 

 rays, antimera) originally connected only by their oral extremities, whereby the central 

 connecting part or disc gains in circumference, as it were, at the expense of the arms, 

 which at last seem entirely to disappear or to be absorbed in the disc. This change is 

 manifested chiefly in the exterior, without, at least in the commencement, being accompanied 

 by any corresponding alteration of the interior organisation. Only at a later period there 

 occur other alterations, chiefly those connected with the digestive system, the main parts 

 of which, originally belonging to each single individual (person), after being thus brought 

 mechanically nearer together, at last undergo a transformation more convenient for the ali- 



