No. 3. — (Letter No. 5.) — To Caelile P. Patterson, Sitjjerin- 

 tendcnt United States Coast and Geodetic Survey, from Alex- 

 ander Agassiz, on the Explorations in the Vicinity of the 

 Tortngas, during March and AjJril, 1881. 



I LEFT Key West for the Tortugas in the middle of March on the 

 " Laurel," which Lieut.-Com. Wright had kindly ordered, in accordance 

 with the permission of the Lighthouse Board, to transport myself and 

 assistant, with the necessary coal for the steam launch which you had 

 placed at my disposal during my visit to the Tortugas. The launch I 

 found ready at Key West, fully equipped, manned, and provisioned, 

 thanks to the care of Lieut.-Com. Winn. She arrived at the Tortugas 

 somewhat later in the day than the Laurel. 



During our stay at the Tortugas we were allowed by the Hon. 

 Secretary of War to occupy such quarters at Fort Jefferson as were 

 not otherwise needed, and selected as a laboratory a large room, with ex- 

 cellent light, on the ground floor of the barracks. We remained at the 

 Tortugas five weeks, and spent the remaining time at my disposal at 

 Key West, where we continued our studies of the pelagic fauna of the 

 Gulf Stream. We returned to Key West in the revenue steamer Dix, 

 Captain Scammon, whom the Secretary of the Treasury had authorized 

 to assist us as far as practicable. 



The prevalence of strong northerly winds during the greater part of 

 our stay in Florida interfered greatly with the work which was the 

 principal object of my visit, — the study of the surface fauna of the Gulf 

 Stream. We expected to find the usual prevailing southeasterly winds, 

 and to find the pelagic fauna of the Gulf Stream driven against the Tor- 

 tugas. In this respect we were greatly disappointed, and I availed my- 

 self of days, otherwise favorable, in finishing a number of drawings of 

 the most characteristic oceanic Tubularians of the Gulf Stream, the Por- 

 pita) and Physalice. I had accumulated a number of drawings and notes 

 either at Newport or on the " Blake," but under circumstances not spe- 

 cially favorable for a critical examination of the specimens. A number 

 of interesting stages of Porpita, of Velella, and of Physalia were ob- 

 served, as well as many points of interest in their anatomy hitherto 



VOL. IX. — NO. 3. 



