of the Polypes and of their Polypary. 41 



up different points of view, have endeavoured to demonstrate 

 the invalidity of these laws and the difficulty or impossibility 

 of verifying or applying them which often exists. 



One of my wishes when I went to Africa this summer 

 was to find embryos and very young individuals of polyparian 

 polypes, and to revise, with the view of verifying them, the 

 various theories put forward as to the origin and mode of 

 growth of polyparies. I was fortunate enough to obtain both 

 embryos and very young polypes ; and I have now the honour 

 to present the results of my new observations to the Academy. 



It is well known that the polype which clothes and produces 

 a polypary presents round its mouth circlets of tentacles or 

 arms of different sizes, that these tentacles have also been 

 grouped in cycles, and that the same series of laws has been 

 applied to their development as to that of the laminae of the 

 polypary. Now, by following the appearance of the tentacles 

 upon the embryo, we cannot verify any of the laws which we 

 find current ; and this I proved in a memoir published last 

 year* . 



This causes great perturbation of mind when we desire to 

 pass from the study of the soft parts of the animal to the 

 knowledge of the development of its hard parts. In fact, each 

 tentacle corresponds to a chamber in the body of the 2)ol_)^e ; 

 and at the bottom of each of these chambers there rises one of 

 the calcareous laminae of the polypary. The question therefore 

 arises at once, whether the chamber and the tentacle belonging 

 to it, as also the calcareous septum which occupies it, follow 

 the same or different laws in their formation. 



I have been able during my voyage to ascertain the perfect 

 exactitude of the following facts. 



Two questions presented themselves. It was necessary, in 

 the first place, to determine in what part and Avhat elementary 

 stratum of the organs the deposition of the calcareous particles 

 of the calice commenced, and then what were the laws govern- 

 ing the appearance and multiplication of the parts of the 

 polypary. 



It was logically necessary, in order to trace the progress of 

 the development of the calcareous parts, to know in the first 

 place, just as in the case of the bones, where the first particles 

 were deposited. 



French authors suppose that it is in the dennis of the body 

 of the polypes tliat the principal deposit takes place, and tliere- 

 fore they give the name of Hderodermi to the group of corals 

 here under consideration ; but it must be remarked that it 



* Archives do Zuologie expi^rinitulak' et g»5nt5rale, vol. i. 1872. 



