VOYAGE FROM NEW YORK TO RIO DE JANEIRO. 35 
ally of low sand banks ; but this morning we have sailed 
past the pretty little town of Olinda, with its convent on 
the hill, and the larger city of Pernambuco, whose white 
houses come quite down to the sea-shore. Immediately in 
front of the town lies the reef, which runs southward along 
o 
the coast for a hundred miles and more, enclosing between 
itself and the shore a strip of quiet waters, forming admi- 
rable anchorage for small shipping. Before Pernambuco 
this channel is quite deep, and directly in front of the town 
there is a break in the reef forming a natural gateway 
through which large vessels can enter. We have now left 
the town behind, but the shore is still in sight ; a flat coast 
rising into low hills behind, and here and there dotted with 
villages and fishing-huts. 
The lecture on Saturday was rather practical than scien- 
tific, on the best modes of collecting and preserving speci- 
mens, the instruments to be used, &c. To-day it was upon 
the classification of fishes as illustrated by embryology ; the 
same method of study as that explained the other day and 
now applied to the class of fishes. " All fishes at the time 
when the germ becomes distinct above the yolk have a 
continuous fin over the whole back, around the tail, and 
under the abdomen. The naked reptiles, those which have 
no scales, such as frogs, toads, salamanders, and the like, 
share in this embrvolooical feature of the fishes. From this 
V O 
identity of development I believe the naked reptiles to be 
structurally nearer to the true fishes than to the scaly rep- 
tiles. All fishes, and indeed all Vertebrates, even the high- 
est, have, at this early period, fissures in the side of the neck. 
These are the first indications of gills, an organ the basis for 
which exists in all Vertebrates at a certain period of their 
life, but is fully developed and functionally active only in 
