06 DEEP SEA FISHES. 
(3X) 
which lack the extraordinary filamentary productions and on which the Lat- 
eral System is evidently of much greater functional importance and develop- 
ment. This will be made evident beyond the need of further remark by 
contrasting Plates F and LXXV. of Dicrolene, and fig. 1 of Plate K, 
and Plate LV. of Bathypterois, with Plate XXXIV. and fig. 1 of Plate 
LXXXI. of Lamprogrammus, Plates XX XV. and LXXIX. of Eretmichthys, 
and Plate LXXVII. of Bassozetus. Another instance that may be noted is 
that of Leucicorus, Plates XXXVIII. and LXXIV. fig. 1, a fish without fila- 
mentary organs, and with few prominently developed sensory papillx, and 
one on which the eyes, probably functional early in life, are lable to deteri- 
oration in older individuals; on this fish the organs of the Lateral System 
attain a maximum size and a paramount differentiation. 
There appears to be no connection between one disk and another, pos- 
sibly it is invisible, on many species but on the more differentiated a very 
evident thread-like connection exists, Plate XLI. figs. 1* and 2* and on some 
of them the more common nerve-like thread is accompanied in its course by 
a considerable number of minute nerves, Plates XX XVIII. fig. 7, and 
XXXIX. fig. 2. Plates XXXIV. figs. 4 and 5 and XLI. figs. 1* and 2* repre- 
sent the more common appearance of the disks on forms in which the devel- 
opment has not been carried to such an extraordinary degree. A transitory 
connection between the disks in certain embryos is mentioned by Allis. 
The main nerve to each disk extends to the back, that is to the inner 
side of the central body and there sends out a number of small branches, 
varying for different disks, individuals and species; these branches distribute 
themselves irregularly through the rounded or oblong centrum, and from it 
into the lateral portions of the fusiform mass upon which it is situated. An 
approximate idea of the manner of the distribution within the fusiform 
transverse body and the included centrum may be gained from fig. 4 on 
Plate XXXV. In this case, Eretmichthys, the number of nervules leaving 
the centrum is comparatively small; it represents an intermediate between 
those cases in which none are to be observed and those like figure 7, of 
Plate XX XVIII, in which there are many. From the anterior and the pos- 
terior edges of the fusiform mass, in some species at least, the nervules pass 
into other masses, one mass at each side of the fusiform. The latter give 
to the disk in its entirety a longitudinally oblong shape, Plate XX XVIII. 
figs. 7 and 3, and Plate XX XIX. fig. 2. Whatever they may have been 
in life these portions of the organ are more opaque and whitish than the 
