BROTULOIDS. 145 
strengthened, the rays being bound together to form a broad rigid oar that 
must be of great advantage in making a sudden dash forward and upward 
(see Plate XXXV., fig. 1, also figs. 2 and 5 showing the processes for attach- 
ment of the muscles controlling the rays). 
Quite generally the membranes of the dorsal and the anal fins are contin- 
uous with the membrane of the caudal fin; examination of the type proves 
Barathrodemus manatinus of Goode and Bean to be no exception to this, 
On some of the genera the eyes are comparatively large; on others they 
are small; and on a few they are rudimentary or absent, as on Aphyonus, 
Typhlonus, and Sciadonus (Plate F, fig. 4). The peculiar conditions appar- 
ent on Leucicorus, Plate XXXVIII., probably indicate deterioration and lozs 
later in life of an eye that in the earlier stages of the individual may have 
been serviceable and normal. 
The Lateral System is well developed on the head; frequently it is im- 
perfect or absent belund the body cavity; in cases it appears to be absent 
from the entire body, and in others, as on Porogadus, several lines of the 
system are to be seen immediately behind the head. Because of the promi- 
nence of the cephalic portion of the system in all the members of the group 
it has been studied on a number of the genera and species for compari- 
sons in regard to derivations and affinities, Plates LXXV-LXXXI. From 
these the comparisons have been extended to various other groups near and re- 
mote. No doubt the system, in addition to its sensory function among shoal 
water types, has become luminous, and possibly in cases electric, at greater 
depths. The peculiar disks in the canals, hardly to be detected in those of 
the shoals, attain much greater development on the bathybial species and, in 
position and arrangement clearly indicating genetic relationship through 
common ancestry, are similar in families that in our systematic arrange- 
ments are widely separated. Compare, for instance, the Berycoids, Plate 
LXXIIL., with the Brotuloids, Plates LXXV., or the Macruroids, Plates 
LXXXII., LXXXIV. The affinities of closely allied species are to be seen 
in comparing the figures of Plate LX XV. with the figures of Plate LX XVI. 
In a couple of the species the nerves have been traced from the disks to 
the brain and from the brain to the disks, Plate LXXVIIH. The com- 
plicated distribution of the nerves and vessels in the disks and between 
them is shown on Plate XXXV., fig. 4, Plate XXXVIIL,, fig. 7, and Plate 
XXXIX., fig. 2. 
10 
