18 



and the internal yolk mass. These calcareous spots are not 

 scattered at random ; there are generally eleven principal ones, 

 five corresponding to the radii or ambulacres, five to the spaces 

 between them, and a central one, the rudiment of the madreporic 

 plate. The five interambulacral plates, which answer to the 

 masticating apparatus in other Echinoderms, approach after- 

 wards nearer to each other, so as to form a ring around the 

 attachment of the peduncle ; whilst those corresponding to the 

 rays recede, and form as it were a second ring outside of the 

 first. In the mean time new spots appear, but instead of form- 

 ing outside of those already existing, they come between the 

 two rings ; so that the ambulacral spots which were at the begin- 

 ning near those of the interambulacral ring, are constantly car- 

 ried further from the centre. The last plate of each ray is 

 therefore the oldest ; a fact by no means extraordinary if we 

 consider that it is connected with the eye, and protects it. In 

 a similar way we see, in the higher animals, the hand formed 

 before the arm and forearm. As the ambulacral plates are con- 

 nected with vision, and the interambulacral plates whh the func- 

 tion of nutrition, their early appearance may be considered as 

 an illustration of the general law, that the most important 

 organs are formed first. 



Mr. Teschemacher observed, that in the Address, which 

 he had the honor of delivering before the Society in 1841, 

 and on several subsequent occasions, he had regretted the 

 neglect, by Geologists, of the study of Mineralogy. That 

 he had considered this study, as regards the unstratified 

 crystalline rocks, the equivalent of Paleontology, as regards 

 the sedimentary stratified deposits ; and that he had no 

 doubt ere long some master-spirit v^^ould derive from Mine- 

 ralogy many of the safest and surest landmarks of Geology. 

 These anticipations have been made good, in some papers 

 read before the Geological Society of France last year. 



Mr. T. gave an account of those papers. First, that of Prof. 

 Scheerer, of Christiania, on some of the minerals in the Granite 

 of Norway, showing the existence of primitive, basic water in 

 them ; which, in the opinion of the Professor, militated against 



