MUSEUM OF COMPARATIVE ZOOLOGY. 379 



of the North Atlantic must have been in a north-southerly direction, and 

 that to this day there is a great northern current of cold water sweep- 

 ing past the eastern shores of the United States ; while the southern 

 branch of the Gulf Stream Hows in a southerly direction, past the western 

 shores of Southern Europe ; so that we may expect a strange mixture of 

 arctic and subtropical animals in the great unexplored depths of the At- 

 lantic, between America and Europe. It is to be hoped that the zeal 

 with which the exploration of the deep ocean has begun may not flag 

 before the whole problem is solved. 



One of the most important results of this year's cruise, though not 

 exclusively derived from deep-sea soundings, deserves a special men- 

 tion in this Report. 



Taught by former investigations, upon other classes of animals, that 

 in their affinities and relative standing organized beings exhibit direct 

 relations not only to the changes they undergo while growing, but also 

 to their succession in past ages, and to their present distribution upon 

 the surface of the earth, I lost no opportunity of ascertaining to what 

 extent these relations may also be traceable among the corals. From 

 their simpler organization, and the less prominent differences which 

 distinguish their numerous representatives, it seemed hardly probable 

 that facts could be ascertained plainly bearing upon these questions; 

 and yet, the moment I proceeded with the investigation, I perceived 

 that there was before me a vast field, thus far entirely unexplored, 

 from the survey of which much valuable information could be se- 

 cured. 



A fortunate circumstance unexpectedly favored my researches. In 

 consequence of injuries to a breakwater adjoining Fort Taylor, a large 

 number of granite blocks, which had been three years under water, 

 were hauled up on shore, and I found them covered with a great num- 

 ber of specimens of different species of corals, in various stages of 

 growth. The surfaces of the granite were still so clean that it was 

 possible to detect the smallest young corals upon them, and to trace so 

 many stages between them and larger ones as to leave no doubt of 

 their specific identity. I made, with the assistance of M. Pourtales, a 

 large collection of these young corals, which I afterwards leisurely 

 compared with one another and with adult stocks of the same species. 

 The result of this comparison I may express in few words : Corals 

 undergo a succession of changes peculiarly their own, and yet hardly 



