ZOOLOGY. 373 



differed much in that region a hundred thousand years ago from what they 

 now are, and consequently that such a calculation could reasonably be made 

 upon the data accumulated by Prof. Agassiz. 



Dr. Weinland called attention to a fact recently observed by him in Hayti, 

 which seems to involve a more rapid growth of some kinds of corals than is 

 generally assumed for this class of animals. In a small coral basin, between 

 the town of Corail and the island of Caymitcs, which is never disturbed by 

 vessels, the water being there much too shallow, he saw several branches of 

 the large Jfadrepora alcicornis projecting above the surface of the water from 

 three to five inches. These branches were dead, for corals always die soon 

 after exposuz-e to the air, while the rest of the stock, as far as it was under 

 water, was in full life. This observation was made in the month of June. 

 The question naturally suggested itself, when did those pieces, which were 

 now above water, grow? 



A fact, to which he alluded on another occasion, at a meeting of the Soci- 

 ety, viz., that during the whole winter season (December, January, and 

 February), the level of the water all along the northern shore of Hayti is 

 from four to six feet higher than during the summer season, being raised by 

 a constant northerly wind during those months, suggested to him the idea 

 that those coral branches, as far as they were above water during sum- 

 mer, might have grown during a single winter of three months only. This 

 would show a very rapid growth of this kind of corals , The fact that the 

 Madrepores, when growing so near the surface, and, as stated above, par- 

 tially uncovered during the summer, very often, in the course of a few years, 

 give rise to small Mangrove islands, between the outside coral reef and the 

 shore, was well known to a native Mulatto sailor, whom Dr. Weinland em- 

 ployed there. As he had observed at a former meeting, there is hardly any 

 change of high and low tide along that shore of Hayti; so that this can have 

 no bearing on the present question. 



Prof. Agassiz also stated that he had, as the result of his investigations, 

 been led to institute the following classification of corals : 



1st. Vegetable Corals. These are Algag, or at least vegetable productions, 

 which in time accumulate in their cellular tissue so much lime as to resem- 

 ble coral, and which form entire islands, as the Tortugas and Marquesas 

 group?, the sands on the shores of which are composed of disintegrated par- 

 ticles of these vegetable growths. 2d. Corals of Bryozoa. The affinities of 

 these are well known. They grow in clusters, and are genuine corals 

 belonging to animals of the lower class of molluscs, and not polyps, though 

 once thus considered. 3d and 4th. The remaining corals belong to two 

 types, genuine corals formed by Polyps and those belonging to Uydroid Acalephs, 

 the Tabulata. The Tabulata are known to be Hydroids by direct observation 

 of the animal in Millepora recently made by Prof. A. in Florida. Of Rugosa 

 no living types are known, and consequently its affinities must be deter- 

 mined by the structure of the solid parts. In this respect the Tabulata pre- 

 sent striking differences from the genuine corals formed by the Polyps. 

 These have vertical radiating partitions, extending from top to bottom, 

 with transverse partitions extending only between two adjoining vertical 

 partitions. In Rugosa this horizontal floor extends across the Avhole cavity 

 of the animal, as in Tabulata; and the radiating partitions are limited in 

 their vertical extent to the space between two horizontal floors; so that 

 their affinities go with the Tabulata, in some of which there are traces of 

 radiating partitions. Besides, in Rugosa, the quadripartite arrangement 



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