120 Mr. J. E. Gray's Outline of an Arrangement of Stony Corals, exhibited in L. selaginoides, where it must be possible to find a great many stages at one time on a single spike, as so many oophoridia occur on it. They must be also very easy to prepare for examination here, — a matter of exceeding difficulty in L. den-ticulatum. In conclusion to these remarks on the oophoridium, two words on the affinities of Isoetes and Lycopodium. It appears to me that this question involves the import which must be attributed to the large spore-sporangia of Isoetes. Are these metamor-phosed branches or not ? In the latter case the affinity would be merely apparent, only inasmuch that both, Isoetes and Lyco-podium J exhibit two kinds of spores. In the former case, how-ever, the affinity would be perfectly proved. The compressed, concentrated stem of the Isoetecs would not be any great evidence against the affinity, since we have become, through Kunze, ac-quainted with the genus Phylloglossum. This is apparently a con-necting link between Isoetes and Lycopodium ; and if A. Braun^s opinion be correct, that Phylloglossum is to be regarded as a Ly-copodium acaule, Isoetes would also have to be regarded as a planta acaulis of the Lycopodiacece. It is readily conceivable that the term stemless plant is not to be taken here in its strictest sense, but rather to be understood as indicating a plant with an abbreviated stem. Lastly, in reference to the import of the germinative spore of the oophoridium, BischofF (Krypt. Gew. 126) has called them spore-bulbels [tubercula sporoidea), and compared them to the bulbels of Arum ternatum and Dentaria hulbifera. It is evident that this has no meaning till we know the whole cpurse of de-velopment. The same applies to the expression receptaculum tuber culiferumy which he applied to the oophoridium. I have preferred the latter name because it is the more simple. [To be continued.] XV. — An Outline of an Arrangement of Stony Corals. By J. E. Gray, F.R.S. &c. About ten years ago, when I arranged the Corals in the British Museum, I was struck with the difficulty of determining with precision the proper situation in the system either of Lamarck or De Blainville, of a large number of the specimens we then possessed, and in the ' Synopsis ' I made some remarks on the variation which accidental circumstances, such as localities, &c., appeared to have on specimens of the same species. Since that period I have examined the collections of corals which have come in my way, and selected for the Museum collection the
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