THE WEST INDIAN FAUNA. T 
cruise our collection of Pentacrini became very extensive; we 
found them at Montserrat, St. Vincent, Grenada, Guadeloupe, 
and Barbados, in such numbers that on one occasion we brought 
up no less than one hundred and twenty-four at a single haul 
of the bar and tangles. We must indeed have swept over 
actual forests of Pentacrini, crowded together much as they 
may have lived, at certain localities, both in Europe and Amer- 
ica, during the palæozoic period. 
The monograph of Allman on the deep-sea hydroids of Flo- 
rida gave us the first intimation of the wealth of forms which 
flourished in deep water, forming, as Allman says, a special 
province in the geographical distribution of the Hydroida. 
The collection was noted for the large number of undescribed. 
species, and. the small percentage which could be referred to 
forms existing on the European side of the Atlantic. 
Previous to the deep-sea explorations we knew only the shal- 
low-water reef corals. The expeditions of Pourtalés, of the 
“ Hassler” and the “ Blake,” have revealed to us a whole fauna 
of simple corals separated from the reef district by a barren 
zone, with not a species in common between the two districts. 
There are now over sixty simple deep-sea corals known from the 
Caribbean district, — nearly as many species as there are from 
the reef area. 
It is natural that, as we pass from the littoral to the conti- 
nental, and finally to the abyssal regions, we should find a grad- 
ual diminution of those physical causes which we are accus- 
tomed to consider as influencing the variation of individuals, 
so that persistent types, as they have been called, may owe 
their origin either to an absence of modifying causes, or to an 
inherent tendency to retain. unchanged their original organiza- 
tion. The animals we dredge from deep water cannot, from 
the nature of their surroundings, be affected, or only in a less 
degree, in the many ways which influence their shallow-water 
allies. We cannot suppose that they are subject at great depths 
to any of the causes which affect so powerfully the changing 
chromatophores of the littoral species; such adaptations as 
those which we find in the animals of the sargasso weed, 
for instance, or the littoral alge, or those living on sandy or 
