JAN. — MAR. 1857.] voyage from E?igland to Madras. 151 
vivid green, but when the animal died it quickly faded. Some au- 
thors affirm that each of the tubercles with which their surface is 
studded, constitutes a distinct animal ; but while admitting its com- 
pound nature I should feel rather disposed to compare these tu- 
bercles or gemmules to the buds on a tree ; in short I consider it 
as one of these remarkable instances where the animal kingdom 
closely approximates to the vegetable, and is in some measure 
regulated by the same laws. In their native element they diffuse 
a strong phosphorescent light for a.distance of several inches from 
their bodies, and their aggregate numbers so illumined the stem of 
the ship, that moderately farge print could be read at midnight. 
As we neared the equator a succession of calms temporarily put 
a stop to our towing experiments, the ship making no perceptible 
way through the water. 
April the 29th in Lat. 22-1 S. Long. 387 W. After so many 
fruitless attempts we were gratified to-night by taking in the net 
three different species of Hyalcea and two specimens of another 
genus *' Cuvieria^^ Fig. 26, the flat Hyalma Fig. 12, was first 
caught about twilight, the other, Figs. 13 and 14, were taken after 
dark until 8 p. m. when the wind became too high. 
Both of these genera belong to the Pteeopoda, a class the 
position of which has much distracted the opinions of naturalists, 
some assigning them a rank second only to the 1st class or 
Cephalopoda, while others have variously considered them 
superior or inferior to the Gasteropoda, or degraded them 
below the level of the Acephalous bivalve. Pteropods being 
provided with fins can traverse the ocean, a faculty they possess 
in common with Cephalopods, and in this particular they might 
be considered superior to the creeping Gasteropod, but when we 
compare their interval conformation, habits and instincts, the Gas- 
teropod is seen to exhibit proofs of a much higher state of deve- 
lopment than the Pteropod, which being destitute of feet or pre- 
hensile organs, cannot creep or attach itself to floating objects. 
Nor is the power of swimming " per se" an indication of high 
organization, it is in fact possessed by some of the Gasteropods 
