A FEW MEDUSAE NEW TO WOODS HOLL. 23 



place and from varying depths and a careful comparison of results 

 afford a rough approximation toward an estimate of the relative 

 abundance of life at given depths as compared with the surface, 

 as well as the varying kind of life at the several depths. 



In the more open ocean and in the region of the Gulf Stream 

 the larger number and variety were obtained almost entirely from 

 the surface. In the regions of No Mans Land, Nantucket, Chatham 

 Ledge, Vineyard Sound and Buzzard's Bay, on the other hand, a 

 greater abundance and variety of medusae were obtained from a 

 depth of from 10 to 15 fathoms in water of 17 to 25 fathoms 

 than from either the surface or the bottom. This was more 

 particularly true in rough water and during midday or in bright 

 sunshine. Surface towing during late evening or on dark days 

 most generally give a much larger average in the abundance and 

 variety of species. 



In a general way these results, which I have often observed 

 also in previous years, confirm the observations of others and 

 tend to establish what may be considered a law of pelagic life in 

 its relations to light and other aspects of surface environment. At 

 the same time it should not be overlooked, that occasionally there 

 seem to be marked exceptions to such a law. I have taken at 

 times these same forms from the surface in almost incredible 

 abundance, so abundant indeed that with an ordinary pail one 

 might take hundreds at a single dip. Whether sexual conditions, 

 as Agassiz has suggested, or some other condition at present im- 

 perfectly known or understood may not be involved it may remain 

 for the future to determine. That sexual conditions alone are 

 determining factors seem to me more than doubtful. I should 

 rather incline to consider temperature or tidal currents as probably 

 important factors in the case, just as it seems to me that prevailing 

 winds and currents account for the presence of large numbers 

 of Aurelia ) Cyanea, or other of the Scyphomedusse, in bays or 

 protected harbors rather than that such segregations are for breed- 

 ing purposes. 



SYRACUSE UNIVERSITY, THE ZOOLOGICAL LABORATORY, 

 September 2, 1902. 



