STICKLEBACKS. 
637 
hand, being wanting. We find a trace of this elongation 
in one of our Sticklebacks, the Fifteen-spined species. 
The other families of the Hemibranchii (the Flute-mouths, 
Fist ula ri idee, and the Trumpet-fishes, Centriscidae) are 
also distinguished from the Sticklebacks by the elonga- 
tion and, in some cases, the coalescence of the first 
four or even the first six vertebras. In this manner 
the forepart of the body receives an increase of strength 
which is still further advanced in the Trumpet-fishes 
by the extraordinary development of the anterior inter- 
spinal bones and by their dorsal expansion into a more 
or less perfect shield, which in the Chinese Amphisile 
has been compared, not without reason, to the carapace 
of the turtles. 
The Flemibranchian group is not particularly rich 
in forms. It contains only a score of known and 
described species. Some of them are so like each other 
that their right to specific rank must still be regarded 
as rather dubious; others, again, are so different that 
a, comparatively great number of genera have been 
established. According to Gill the group contains 11 
genera, distributed among 6 families. Most of the fa- 
milies live in the tropical seas; the Scandinavian fauna 
possesses only one. 
Fam. gasterosteid m. 
The anterior vertebrae of normal structure. Ventral fins with one spinous and one or two soft raps. In front of 
the soft-raped ( second ) dorsal fin 3 — 15 free spinous raps ( not united bp a fin-membrane) ; in front, of the anal 
fin one spinous rap. Suborbital ring united to the preoperculum, but without rigid, connexion. Teeth on the inter- 
maxillarp bones and in the lower jaw; palate and tongue unarmed. No scales proper. Base of the caudal fin 
narrow, but, depressed. Branchiostegal raps 3 on each side. Air-bladder simple. Pseudobranchiae more or less 
well-developed ; pploric appendages wanting or rudimentarp. 
Within this family, which was founded by Gun- 
ther/" and originally ranged by him at the head of the 
system of the Teleosts, are collected the Hemibranchii 
in the exterior of which the ordinary piscine form is 
most typically persistent. Still these fishes show ten- 
dencies of transition to the carapaced Trumpet-fishes and 
also to the elongated Flute-mouths. An expression of 
this may be found in the proposed generic division of 
the family. One species, our common Three-spined 
Stickleback, with its well-developed dorsal plates and 
shorter form of body, especially of the snout, has been 
employed as the type of a distinct genus, the true 
Stickleback genus ( Gasterosteus ), while another species, 
the Fifteen-spined Stickleback, with its more elongated 
form and, in particular, its longer snout, is the single 
representative of a second genus, Spinachia or Gastraea. 
The latter genus is approximated to the Flute-mouths 
not only by the form of the body, but also by the 
structure of the pelvic apparatus, which in the Fifteen- 
spined Stickleback is broken up into its two halves, 
which merely meet each other by means of foliate 
processes in the median line of the belly. 
All these fishes are of small size, but have long 
been famous both for their beauty and for the high 
degree of instinct that guides them in the propagation 
of their species. In spite of their insignificant size 
they are not destitute of importance. The gregarious 
habits of some species collect them in such enormous 
masses that they may easily be applied to industrial 
purposes. On the other hand, they are destructive 
enough, for their fatness is gained to a great extent 
at the expense of the fry and eggs of other fishes. 
The range of the family embraces the northern parts 
of both hemispheres. Some of these fishes occur both 
in fresh water and in the sea or, at least, in brackish 
water; but the first genus we shall here describe, is 
exclusively marine. 
Cat. Brit. Mas., Fish., vol. I, p. 1. 
