N.AET! ATIYE OF THE OBFISE. 
“ The numerous species of Sergestes together with those of the allied forms Acctos 
ancl Leucifer exist everywhere in the ocean within a few fathoms of the surface, from the 
cold temperate regions of the north to those of the south. Of the genus Acetes I have 
not seen an indubitable specimen in the collection, but in the locality from which the 
type, first described by Milne-Ed wards, was taken, Sir Walter Elliot records it as being 
abundant, and forming the staple food of some of the larger species of fish that frequent 
the Bay of Bengal. In Leucifer the posterior two pairs of walking legs have entirely 
disappeared, although the penult pair is present at one stage of its existence. Four or 
five species of this genus have been named by authors, but a close analytical examination 
of all the numerous specimens brought home by the Challenger, enables me to determine 
with confidence that the several forms described are but different stages in the sjowth 
of two species, or perhaps only two varieties of the same species. 
“ When the ocean is searched at a depth greater than 100 fathoms the true Permits 
and its gallant congener Aristeus are found to exist in more or less abundance. These, 
if we may judge from the uniform appearance of the long sweeping pleopoda, are 
powerfully swimming animals, and the form of Aristeus with its long and slender 
rostrum, its narrow and compressed condition with polished surface, shows that it is 
capable of swimming through the water with considerable velocity ; when at rest, the 
large and leaf-like scaphocerites are probably extended laterally on each side in the 
water. The rostrum, which is generally long and powerful in several genera of this 
division, acts not only as a sharp cutwater but probably also as a weapon of offence. 
The genus Sicyonict appears to have the scaphocerite especially formed for attack, and 
instead of being broad and leaf-like, flexible and membranaceous, has the outer margin 
developed as a long and powerful spear, and the inner division tapers towards the 
extremity into a plate of extreme tenuity; this organ with its strong and spear-like point 
is under the animal’s control, becoming when fixed a strong and formidable bayonet-like 
weapon of offence, or when relaxed a harmless balancing organ. 
“ A similar offensive weapon is formed by the telson of the genus Glyphocrangon, 
which is a rigid, sharp-pointed, and powerful organ. This the animal has the power of 
locking and unlocking at will, and according to its size and power is capable of striking, 
scorpion-like, with much force, inflicting thereby no slight wound. 
“ Such genera as Gennadas and Benthesicynms (see fig. 185) dwell apparently in deep 
water, probably far beneath the predaceous pelagic animals. The former seems to lose 
the osseous texture of its integument, and with it all power of defence. The eyes 
become less brilliant through the diminishing quantity of black pigment, while the small 
phosphorescent organ increases in size and value. With the exception of Glyphocrangon, 
which is a powerful combatant, all the animals brought from great depths are soft and 
flexible creatures, being incapable of attack or defence. 
“ That the existing species of Crustacea live, each of them, within certain limits 
(XARR. CHART.. EXP.- — VOL. I, — 1885 .) 57 
