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POPULAR SCIENCE REVIEW. 
slender tail, marked on each side with a small ridge (a character 
which also occurs in the adults), and furnished with a very small, 
entire fin. On each side of the head is a large, round eye, and 
in front of this the forehead of the little fish descends rapidly to 
the base of a slightly projecting beak, which, however, is not so 
long as the diameter of the eye. The beak includes both jaws, 
and the upper jaw is very little longer than the lower one ; the 
jaws open quite back under the eyes, and both of them are 
armed with comparatively strong teeth, those at the apex of the 
jaws being stronger than the rest, and curved. The spine 
springing from the prseoperculum is much longer than the short 
round pectoral fin, and the edges of this and of the parietal 
spine are finely serrated. Small spines occur both above and 
below the prseopercular spine, and over each eye there is a small 
supra-orbital spine, which, however, disappears very early. Be- 
sides the pectoral fins, which show indications of rays, and the 
caudal already mentioned, there are rudimentary dorsal and 
anal fins, consisting simply of membrane, with no trace of rays. 
It will be easily seen that such a little creature as this 
has scarcely any resemblance to the adult swordfish ; and, indeed, 
Dr. Liitken says that but for the previous knowledge 
of the developmental stages of these fishes, his youngest 
forms would rather have been referred to some fish allied 
to the Flying Giurnards (Dactylopterus). This youngest stage 
is made known by one of a series of small fishes advancing 
from rather more than one-fifth of an inch to rather less than 
half an inch long ; and the whole of these, Dr. Liitken says, 
differ very little from each other, the principal difference ap- 
parently being that the younger the fish, the shorter and 
broader is its little beak. Nevertheless, the largest of Dr. 
Liitken’s earliest series exceeds in length the specimen on which 
Dr. Gunther’s first stage was founded, as this was only 9 milli- 
metres (rather more than one- third of an inch) long, although 
it already shows signs of a more advanced development. The 
general form of the fish more nearly resembles that of the adult, 
although the head and eyes are still of rather disproportionate 
size ; the forehead still falls abruptly in front of the eye ; but 
the beak is comparatively longer, although the jaws are still 
nearly of equal length, and armed througnout with teeth. The 
spine above the eye, and the small spines on each side of the 
pra;opercular spine have apparently vanished ; the prseopercular 
spine itself is comparatively longer than in Dr. Liitken’s earliest 
form ; the dorsal and anal fins form low but distinct fringes, quite 
separate from the caudal, which is already rayed and forked; and 
beneath the pectorals small rudiments of the ventral fins have 
made their appearance. In a second stage, a fish, but little more 
than half an inch in length, is described and figured by Dr. Gun- 
