to Central America. 3931 



they looked like small birds, but, glittering in the sun, presented a sin- 

 gularly airy aspect, their fins becoming nearly invisible. 



March 8: (lat. 21 57; long. 32 13). The sea is most beautifully 

 phosphorescent this evening ; thousands of sparks — some yellow, 

 some green, some red, and of different sizes — are shining in the white 

 spray caused by the ship's rapid course through the waves. The sea 

 near the vessel has the aspect of a black sky, on which are floating 

 fleecy snow-white clouds, through and around which hundreds of stars 

 are twinkling with surprising brilliancy. The clear moon, on rising, 

 puts out the animated stars of the ocean, and at the same time eclipses 

 the light of the celestial ones ; Venus alone, throwing on the waters 

 her long ray of silvery glow, does not shrink before the glaring disk. 



March 9 : (long. 33 23 ; lat. 21 15). Four large Cetaceans passed 

 slowly alongside our vessel : their length was about 20 or 25 feet ; 

 the back and hinder part of the very convex head were alone out of 

 the water, the blow-holes very far back ; the back was dirty brown, 

 the nape and head being grayish. These animals blew the air through 

 their spiracles, so as to produce a loud snorting sound, but did not 

 eject any water. They were, I believe, some species of Globicepha- 

 lus, perhaps G. fuscus, which is unknown to me otherwise than by 

 name. 



March 10 : (lat. 20 31 ; long. 36 54). I fished up two pretty Me- 

 dusas, of the family Oceanidae, about 2 inches long, with vermilion- 

 coloured nucleus ; also some fine specimens of Velella, which were 

 floating in great numbers on the surface of the calm sea, in company 

 with Physalisa. These singular Siphonophorae are of a fine blue co- 

 lour when living, but change to yellowish brown in spirits. I believe 

 I can distinguish two species, by their size and the shape of the dorsal 

 cartilaginous plate : the smaller one having it triangular ; the larger, 

 oval-oblong. The Velella can float on its back, making use of its 

 under side (as would a gasteropodous mollusc of its foot), so as to form 

 a vacuum : it is, however, generally seen with its carina uppermost. 

 Empty shells of Spirula are common, floating on the surface of the 

 waves ; as also a fine species of compound Salpa, with blue nucleus. 



March 12 : (lat. 19 45; long. 37 32). Many large flying fish {JExo- 

 cetus volitans) appeared today. Several small white birds were ob- 

 served at a distance, but did not come near enough to be recognised. 



March 13: (lat. 18 44; long. 39 21). Exocetus volitans very fre- 

 quent. I still see patches of Fucus natans ; this is more than three 

 degrees further South than is indicated by botanists. I caught a 

 small isopodous Crustacean, of a shining steel-blue colour ; the 



