246 Van Beneden on the genera Elevitheria and Synhydra. 



proofs of infinite variety in the works of nature. Although the 

 superior animals are only produced after their complete develop- 

 mentj we have thence no right to conclude that the lower ani- 

 mals are similarly circvimstanced. 



We have no doubt that the new animal named Eleiitheria is 

 the first stage of a polyp allied to Tubularia. Even the other 

 characters peculiar to this genus furnish new proofs in favour of 

 what we have stated. 



The Eleutheria has the eyes at the base of each of the tenta- 

 cles. Some years ago importance might have been attached to 

 this character, as in general larvre do not possess these organs ; 

 but the organ of vision has now been observed in several of these, 

 and even solely in this first stage. In the Campanularia we have 

 seen as many as eight eyes dm'ing the time that the polj^ is free, 

 but in its medusa-like form these organs of relation disappear. 

 Thus here the reverse happens of what occurs generally in the 

 other classes. Being young, these polyps enjoy their full and en- 

 tire liberty ; they move about as long as they are larvae, but as 

 soon as they become perfect they only vegetate ; they fix them- 

 selves on some body, — their condition becomes wholly passive ; 

 and the functions are limited, as in plants, to nutrition and re- 

 production. 



The arms or tentacles have been investigated with great care 

 by M. de Quatrefages. As the author himself admits, they are 

 perfectly similar, with respect to their composition, to those of 

 the Syncorynes. These tentacles are bifurcate, and here we find 

 another relation with the Eudendrium. They become in fact di- 

 vided imder our eyes in this genus, and the four become eight. 

 The Eleutherice approach the larvae of the Syncorynes in general 

 form, but we have observed the separation of the tentacles only 

 in Eudendrium. 



Each arm terminates in a kind of rounded cushion which we 

 have observed in the genera which we have just cited ; but this 

 swelling has, in our opinion, no other object than to permit the 

 extension of the tentacle, and we have always seen them disap- 

 pear when this organ was completely expanded. They are in 

 reality merely the eff"cct of the contraction and of the agglo- 

 meration of the cellides; this is at least the opinion we have 

 come to. 



A difi'erence which we have to indicate is, that we have not per- 

 ceived in any one of the genera the spiculiferous sacs which M. de 

 Quatrefages has noticed on the arms of the Eleutheria. He has 

 represented them as seen with a magnifying power of 900 dia- 

 meters. We have rarely employed a power of more than 300 or 

 400, and this is probably the reason we have not noticed them. 



Whatever be the difference, it does not seem to us improbable 



