628 SUMMARY OF CURRENT RESEARCHES RELATING TO 
directions. Mr. Alcock’s work ought to prove of great value to students 
of this division of the Animal Kingdom. 
Stalk-Eyed Crustacea of the ‘Albatross.’* — Mr. W. Faxon has a 
report on the stalk-eyed Crustacea collected during the voyage of the 
‘Albatross’ in 1891. After a systematic account of the species, a 
number of which were found for the first time by this expedition, the 
author proceeds to some general considerations on distribution. The 
route of the ‘ Albatross ’ extended over 29 degrees of latitude, and the 
bathymetrical range explored was very great, extending as it did to 
2232 fathoms. Although there is no definite line dividing the littoral 
from the deeper fauna, it is convenient to consider them separately. 
All writers have recognised that the temperature of the sea is the chief 
factor which governs the distribution of marine Crustacea. It is true, 
as Gill well says, that the relations between the littoral marine faunae in 
a longitudinal direction are traversed and compdicated by relations 
existing in a latitudinal direction. This is due to the easy routes of 
migration afforded by the great coast lines and from the dispersal of the 
larvae of tropical species northward and southward by the deflected 
equatorial currents. On the whole, however, the change of temperature 
has proved a barrier to the spread of tropical littoral species northward. 
Every summer myriads of delicate larvae are borne on the warm bosom 
of the Gulf Stream to the southern shores of New England, only to perish 
on the approach of the northern winter. Littoral species of the cold and 
temperate zones have this advantage over tropical types in the matter of 
distribution on north and south lines, that the temperature of the sea 
rapidly falls in passing from the surface downward, so that even under 
the equator a temperate degree of heat is found at a moderate depth* 
Avoiding the fatal heat of the tropics certain species of the temperate 
zones have actually passed under the equator and invaded the opposite 
hemisphere. This, of course, has been already remarked by students of 
other groups than Crustacea. 
A list is given of the similar littoral species of the Panamian and 
Caribbean provinces. Few of the characteristically Indo-Pacific genera 
are found in the Panamian province. Below the littoral zone there lies 
a belt extending, say from 150 to 500 fathoms, which forms a sort of 
debatable ground, invaded, on the one hand, by littoral types from 
above, and, on the other, by characteristic deep-sea forms from below. 
A list of the genera found below the 500 fathom line shows the 
enormous, even cosmopolitan, distribution of deep-sea types and their 
lack of special affinity with the nearest littoral fauna. This is shown 
by a comparative list. Deep-sea Crustacea do not seem to be divisible 
into subordinate local provinces, like those of the littoral and terrestrial 
faunae. It is manifestly illogical to assume, as some have done, that 
because a certain form is now restricted to deep water the rocks in which 
it occurs as a fossil were deposited at a similar depth. The surviving 
representatives of an ancient shallow water type may be littoral, as in 
the case of Limulus , or they may be found only in deep water, like the 
recent Eryontidse. Some unquestionable bottom-living species at the 
present day have a vertical distribution of 2000 fathoms. The small 
Mem. Mus. Comp. Zool., xviii. (1895) 292 pp., 56 pis., 1 map. 
