600 
SCANDINAVIAN FISHES. 
not only with its own vertebra, but also with the 
fourth. The ribs of the latter have assumed the form 
of disks united to its back. In Fierasfer dentatus the 
third pair is only slightly extended, the second and 
first pairs all the more so, though far less than the 
third pair in the former species. To these bones is 
attached the anterior part of the air-bladder — which 
extends along- the whole dorsal wall of the abdominal 
cavity, which is much broader in acus than in dentatus 
— and here are extended muscles to draw the air- 
bladder forward, among which the median are especially 
large and powerful, originating from and coasting the 
parasphenoid bone and attached to the anterior end of 
the air-bladder. 
The eggs of these fishes are developed floating- 
in the sea, united within a slimy mass, like those of 
the Angler. Of the spawning (deposition of the eggs) 
we know only that it takes place at night. The deve- 
lopment advances quickly. By the sixth day the yolk 
is absorbed, and the larva begins to eat. It is now 
only 3 or 4 mm. long, but already Eel-shaped, and, 
in Fierasfer acus , has a singular appendage on the 
back, almost as long as itself. This is the first- ray 
of the future dorsal fin, which has early grown into a 
long, stiff stem, with foliate growths set alternately. 
Mere we again meet with an example of the long- 
appendages which we have already observed on several 
occasions in the larvae of pelagic fishes, and which help 
the larvae to support themselves as they float in the 
water and drift with the current. These appendages 
probably give the larvae a protective likeness to small 
Medusae, and perhaps, as Emery supposes, serve as a 
lure to entice the small crustaceans ( Entomostraca ) on 
which the larvae live". This evanescent growth does 
not appear in the larva of Fierasfer dentatus , in which, 
on the other hand, the body is still more elongated 
and resembles a long, narrow ribbon''. In the case of 
this larva Emery has also made the observation that if- 
possesses a considerably greater number of vertebrae 
than the full-grown fish, which generally has only 95 
vertebras (26 abdominal), while in one larva he found 
175 vertebras. In adult specimens of Fierasfer dentatus 
too, the tip of the tail is often broken off short, and 
bears a secondary growth, corresponding to a caudal 
fin, such as we have above seen to be common among 
the Macruroids. Emery was therefore quite justified 
in his suspicion c that Fierasfer dentatus in later years 
discards its shelter within the sea-cucumber, or at- all 
events cannot gain entrance in the same manner as its 
congener, although he subsequently^ met- with a small, 
but full-grown specimen (with 115 vertebras) in a 
Holotharia tubulosa. 
Genus FIERASFER. 
Pectoral fins present e . Branchiostegal rags 7. Pseud obranchice wanting. Branchiostegal membranes united under- 
neath , but free from the isthmus. The upper jaw projects slightly beyond the lower. (Jar diform 1 teeth, in the 
jaws , on the vomer , and on the palatine bones. Anal aperture nearly vertically below the insertions of the 
pectoral fins. Pyloric appendages rudimentary . 
This genus seems t-o attain the highest point of its 
development in Indo-Aust-ralian Avafers, Avhere 5 or 6 
species are knoAvn. One species has been described 
from the east coast of Africa, one from Central Ame- 
rica-, and t-wo from Europe. In 1853, during the voyage 
round the world of the frigate Eugenie , Professor H. 
Kinberg took near the Keeling Islands specimens of 
Fierasfer parvipinnis 31 cm. in length and Avit-h a- 
depth of 23 mm. just behind the head. The other 
species of the genus are considerably smaller. 
a In Kaup (Ann. Mag. Nat. Hist., ser. 3, vol. VI (1860), p. 272, tab. Ill, fig. D) this larva has borne the name of Porobranchus 
linearis , in Gasco and subsequently in Costa (Anuario del Museo Zoologico di Napoli, Anno V, tav. I, fig. 1) that of Vexillifer de Filippi. 
b Another characteristic, as yet observed only in the larva of Fierasfer acus, is that the tip of the tail ends, as in the Macruroid 
larvae ( Krohnius ), in a long, filamentous prolongation. 
0 Fn., FI. Golf. Neap. II, Monogr. Fierasf., p. 18. 
d Mitt-h. Zool. Stat. Neap. Ill, p. 282. 
e Though sometimes small. 
f Sometimes set in one row in tire jaws. 
