o 



24 Miscellaneous. 



which the transverse dimensions of the calyx are the smallest rela- 

 tively to the diameter of the peduncle. If we consider that in the 

 existing free Echinoderms the whole body only represents the calyx 

 of the attached Crinoids surmounted by its arms, we are astonished 

 to see a part which is absolutely nil in the representatives of the 

 other groups acquire in Demoerinus so great a development that it 

 represents at least five or six times the volume of the body properly 

 so called. This fact alone warns us that the peduncle must be 

 regarded as of great importance in the determination of the funda- 

 mental form in the Echinodermata. In Demoerinus it produces a 

 radicular apparatus formed of ramified articulated branches having 

 the same structure as itself, and presenting dimensions superior to 

 those of the arms : this apparatus cannot be neglected from a morpho- 

 logical point of view ; and one is led to regard its different branches 

 as having the same value as the peduncle itself, of which they 

 possess the structure. 



in one of our Democrini the peduncle furnishes two bundles of 

 roots and becomes slightly attenuated in the region where these 

 appeadages originate ; but it afterwards resumes its primitive di- 

 mensions; and we cannot avoid inquiring whether the part which is 

 produced beyond the roots is not destined to become a second pe- 

 duncle surmounted by a second calyx. If this induction should be 

 verified, the Democrini will constitute the first existing example of 

 Echinoderms living in colonies and ramified. 



In a former work * I have shown that there exists a striking 

 parallelism between the Echinodermata and the Ccelenterata with a 

 radiate structure. Under the empire of a determinate condition of 

 existence, namely fixation to the ground, the Coelenterata form 

 arborescent colonies upon which modified polyps group themselves 

 in whorls, just as the leaves of plants do to produce flowers, and 

 thus give origin to radiate organisms, Medusae or Coralliarian 

 polyps. 



The greater number of the primitive Echinodermata were fixed 

 to the ground ; the existing Echinodermata are all radiate ; it was 



natural to conclude that the same condition of existence had led, by 

 the same mechanism, to the formation of organisms presenting the 

 same mode of symmetry in the two groups of the Coelenterata and 

 Echinodermata. But the series of Echinodermata wanted the arbo- 

 >cent forms, which are the starting-point of all subsequent evo- 

 lution in the Coelenterata. The Democrini evidently serve greatly 

 to diminish this gap. Even if they did not live in colonies, the con- 

 siderable bulk of their branched roots, the resemblance of these roots 

 to the arms which surmount the calyx and with which -they are 

 probably homologous, suffice to demonstrate that the arborescent 

 arrangement of parts, which is in some sort a preface to radial sym- 

 metry, is not more foreign to the type of the Echinodermata than to 

 the type of the Coelenterata.— Comptes Bendus, February 12, 1883, 

 p. 450. 



* Les Colonies Animale3 et la formation des Organismes. 



