MACRUROIDS. 193 
the fact of remaining on or near the bottom, sufficiently account for fre- 
quency of capture. The species themselves are mostly of local distribution, 
and it is altogether probable that most if not all of those to which wide 
distributions have been assigned will yet have to be subdivided. 
The greatest depths from which up to this date Macruride have been 
obtained are the following: 1825 in the northeastern, 1875 in the north- 
western, 2160 in the southeastern, and 2425 fathoms in the southwestern 
parts of the Pacific ; 2327 in the northeastern, 1870 in the northwestern, 
and 2650 in the southwestern portions of the Atlantic; 1575 to 1950 in the 
Antarctic, and 1310 fathoms in the northern sections of the Indian Ocean. 
As may be seen in various cases in the subjoined list, the vertical range 
of a single species is sometimes more than one thousand fathoms, in one 
instance, that of Nematonurus armatus Giint., more than two thousand, which 
indicates conclusively enough the ineffectual nature of pressure as a barrier 
in the vertical distribution of species. If the general adaptability of tissues 
and structure to changes of conditions is considered, there is no evident 
reason for surprise in the fact that individuals of a species are comparatively 
indifferent to variations in pressure corresponding to hundreds or thousands 
of fathoms of depth. Similar adaptiveness to variations in temperature is 
no doubt possessed by most forms. 
So far as known modification by life at great depths includes the 
acquisition of no special organs among the Macruridz, The eyes of some 
are enlarged, none of the known species are blind, but no special luminous 
organs appear. The canals and glands of the lateral system have become 
much enlarged and have assumed much greater functional prominence, appar- 
ently without much change in structure, yet it is probable that the mucous 
is more phosphorescent and that the glands have become flash organs in 
various species. Some of the species have filamentary growths on the fins, 
and in those from the greater depths the armature and the tissues are less 
firm. The changes in the skull on account of enhanced function of the 
lateral system are amply set forth on Plates L. and LI., the greater amount 
of modification existing in the ridges inclosing and protecting the organs 
of that system. 
Among the species described below there are close allies of Coryphenoides 
Bairdii and C. carapinus, but all told the affinities are little closer across the 
Caribbean with species of the Atlantic than across the Pacific with others 
described by Alcock from the northern parts of the Indian Ocean. 
13 
