DÉVELOPPEMENT DES CORALLIAIHES. 287 



ments, et une figure qui représente les cloisons membraneuses, 

 rapprochées deux par deux et groupées par cycles régulièrement 

 disposés (ttiere are six pairs in the fîrst séries ; six in the second : 

 ficelve in the third ; twenty-four in the fourth ; forty-eight in the fifth, 

 and so on). 



Nous rapporterons le passage en entier relatif à la symétrie bila- 

 térale , car il permettra de rappeler les travaux des zoophyto- 

 logues les plus accrédités d'Amérique, qui ont parlé de la bilaté- 

 ralité. 



Quoique les polypes soient de vrais Radiaires, dit M. Dana, ils ont 

 quelque peu de la polarité antéro-postérieure, qui est manifestée par 

 des raies colorées sur le disque, des tentacules plus développés, et 

 par la possibilité de diviser les animaux en deux moitiés latérales par 

 un plan, passant par le grand diamètre de la bouche. Je cite textuel- 

 lement : 



« Although polyps are true Radiâtes, they hâve something of the 

 antero-posterior (or head-and-tail) polarity, with also the right-and-left, 

 which is eminently characteristic of the animal type. This is mani- 

 fested in the occurrence in some polyps of a ray on the disk différent 

 in color from the gênerai surface : of one tentacle larger than the 

 others,and sometimespeculiar in color; of two opposite septa in cali- 

 cle or polyp-cell larger than the others, and sometimes meeting so as 

 to divide the cell into halves. The first of thèse marks the author 

 has observed in a Zoanthid, as mentioned in his report on Zoophytes 

 at page 419, and represented on plate 30 : and the last in ver) 

 strongly developed in the cells of many Pocilloporœ [ib., p. 523). 

 Gosse and many other authors hâve drawn attention to the one large 

 tentacle, and the fact that it lies in the direction of the line of the 

 mou th. Prof. H. James Clark, in his Mind in Nature states that the 

 order in which the fleshy septa and the tentacles in an Actinia are 

 developed has direct référence to the right and left sides of the body, 

 and that there is only one plane in which the body can by divided 

 into two halves, and this is that corresponding with the longer dia- 

 meter of the stomach, or the direction of the mouth. M. A. Agassiz 

 has shown that in Actinia^ of the genus Arachnactis, the new septa 

 and tentacles are developed either side of the one chief or anterior 

 tentacle; and Prof. Verrill, that in Zoanthids, they are formed prin- 

 cipally either side of this anterior tentacle and also of the opposite or 

 posterior one, and much less rapidly, is at ail, along the sides inter- 



