MUSEUM OF COMPARATIVE ZOOLOGY. 383 



young Meandrina passes from a Fungian into an Hydnophora state, and 

 in its farther extension, which takes place when the community has about 

 two inches in diameter, when the trenches and walls begin to curve, 

 while the margin is still spreading horizontally, the young Meandrina 

 assumes the appearance of an Aspidiscus, a genus of the cretaceous 

 period ; in truth, it then resembles Aspidiscus and Hydnophora more 

 than any adult representative of its own genus. We have here the 

 highest complication of the Astrasoid type, exhibiting successively 

 Fungian characters, common Astraea characters, Hydnophora charac- 

 ters and Aspidiscus peculiarities, before it assumes its own prominent 

 and permanent features. The Turbinolian stage I have had no oppor- 

 tunity of observing in Meandrina. This genus seems to grow more 

 rapidly than other Astrasans, and it was with difficulty I secured the 

 earlier Astrrean and Fungian stages of its growth. 



Zoologists are so accustomed to consider the Oculinidce and Madre- 

 poraidce as branching corals, that they may be surprised at the announce- 

 ment that these families, like the Astrseans, have their spreading Fun- 

 gian-like stage of growth, — and yet I have before me a complete series 

 of Oculina stocks, among which small clusters of individuals in simple 

 juxtaposition exhibit the earliest condition thus far observed ; others con- 

 sist of flat spreading disks, several inches in diameter, without a verti- 

 cal branch ; while in others the branches seem to rise as small knobs 

 and then begin to assume the ramified forms under which the Oculinas 

 are generally represented in our museums. Even our most branch- 

 ing Madrepores, such as Madrepora prolifera and cervicornis, form 

 spreading disks before they rise into branching stocks. Madrepora 

 palmata is, as it were, an overgrown embryonic condition of the rami- 

 fied species. 



This summary of the facts concerning the growth of our coral-stocks 

 can leave no doubt respecting the correspondence of the phases of growth 

 of the Polyps and the gradation which may be recognized in full-grown 

 communities of these animals. If we extend these comparisons to the 

 representation of the class in earlier geological periods, down to the 

 present time, we cannot fail to perceive that the series exhibiting their 

 succession in time coincides also with that of their relative standing and 

 that of their growth. In order to make this plain it would be necessary 

 to enter into a discussion upon the real affinities of corals, for which 

 this is not the place. I would state, however, that the knowledge I have 



