THE SPONGES COLLECTED IN PORTO RICO IN 1899 BY THE U. S. FISH 
COMMISSION STEAMER FISH HAWK. 
By H. V. WILSON, 
Professor of Biology in the University of North Carolina. 
The following - report has been put, at the request of the Commission, in such shape 
that it may be used for the identification of forms by those unprovided with the special 
literature bearing on the different species. Some description of each species, whether 
known or new, is therefore given. The descriptions in all cases apply particularly 
to the collection specimens. It has seemed unnecessary to give complete lists of the 
synonymy. Under each species reference is made to the memoir containing the 
original description. The additional references are to works in which important 
redescriptions have been given, and which for the most part are readily accessible. 
It is needless to dilate on the limitations imposed on one who undertakes to describe 
a collection of sponges. The histological condition of the material is, of necessity, very 
poor. Many specimens are broken; and frequently a species is represented by but a 
single specimen. Species founded on such data are, of course, provisional. Subse- 
quent study of the animals in their habitat, particularly observations on the individual 
differences due to mere locality, age, or regularly recurring physiological condition 
(for example, alteration in the surface associated with the closing and opening of 
pores and oscula), will naturally lead to a more precise conception of the systematic 
position of those forms, of which the collection specimens are examples. 
The question whether a specimen or two, differing in certain respects from a 
described species (itself frequently based on a study of a very small number of 
preserved specimens), is to be recorded as a new species or as a variety is one as 
familiar as vexing. Where in the sponges the difference is one of shape only (as in 
the cases of Pilochrota fibrosa var. globular if or mis, p. 385, or Aplysina flag elliformis 
var. anomala , p. 107), even though this difference be a very considerable one, there can 
be no doubt that it is right to group the differing forms as varieties, round a type 
form having the same skeletal elements and arrangement, canal system, and histo- 
logical structure; or indeed to merge them in the type. Where, as for instance in 
the case of Ilircinia faitida var. cmpidata (p. 106), the differences are slight but 
definite, and concern various parts of the anatomy, the question becomes more com- 
plex and is obviously one that must be decided in each particular case from the 
standpoint of expediency. In cases of this sort, where we do not know whether the 
individual peculiarities are inheritable, and thus racially distinctive, or whether 
the offspring of the “varying” forms start afresh on the same footing with those of 
the type, the term variety clearly can have no precise meaning. This fact does not, 
