224 THE ZOOLOGIST. 
the Weaver (T'rachinus), in which the dorsal and opercular 
spines have the same function as the caudal spines of the Sting: 
rays; however, in the Weavers the spines are deeply grooved, 
the groove being charged with a fluid mucus. 
Passing to the chapters which deal with the distribution of 
existing fishes over the earth’s surface, we come to one of the 
most interesting portions of the work, and, from a scientific point 
of view, one of the most valuable. 
In attempting to draw the line between marine and fresh- 
water species some difficulty is experienced, inasmuch as there 
are some which can gradually accommodate themselves to a 
sojourn in either salt or fresh water, and others which seem quite 
indifferent to a rapid change from one into the other; so that 
individuals of one and the same species may be found some dis- 
tance out at sea, whilst others live in rivers far beyond the in- 
fluence of the tide, or even in inland fresh waters without outlet 
to the sea. 
Eliminating what may be termed the brackish water forms, 
Dr. Giinther tabulates (pp. 208, 209) the true fresh-water fishes, 
of which he recognises 2269 species, and the marine fishes (pp. 
255—811), which he divides into Shore Fishes, Pelagic Fishes 
(inhabiting the surface and uppermost strata of the open sea), and 
Deep-sea Fishes. Some idea of the vastness of the subject may 
be formed when it is stated that of the principal types’ of shore 
fishes alone, more than 3500 species may be enumerated. 
To work out the geographical distribution of all these, as Dr. 
Giinther has done, must have necessitated an expenditure of time 
and laborious research truly astonishing, and the result is the 
more to be valued, inasmuch as no previous writer on Ichthyology 
had attempted such extensive generalisations. 
We should like to give some extracts from the chapter on 
Deep-sea Fishes (pp. 296—311), which is one of the most in- 
teresting in the whole volume, particularly as the knowledge of 
the existence of deep-sea fishes is, comparatively speaking, one of 
the recent discoveries of Ichthyology, for until the voyage of the 
‘Challenger’ not more than thirty species were known. But the 
subject is one which cannot be discussed in a few lines, and we 
must therefore recommend our readers to peruse this chapter in 
its entirety. They will find in it a summary of the present state 
of knowledge respecting deep-sea fishes, and an interesting 
