258 OF THE DEEP-SEA CRUSTACEA 



waters have been modified to meet the peculiar 

 circumstances — depending on increased pressure, dark- 

 ness, persistent low temperature, and deficiency of 

 oxygen — of their own world, using Indian species to 

 illustrate the argument. 



First, as regards persistent cold : in the seas of 

 India the winter temperature of the surface water is 

 from 80° to 85° Fahr., while at a depth of 100 

 fathoms it is only about 60° Fahr., and at 1000 

 fathoms it is less than 40° Fahr., whence it follows 

 that, were temperature the only consideration, forms 

 that live in high northern seas could exist equally 

 well in the cool depths of the tropics. Of course 

 the matter is not nearly so simple as this, yet — as 

 revealing tendencies — we do find in these depths a fair 

 number of crustaceans that, until recently, have been 

 regarded as characteristic of northern temperate seas : 

 such are the crabs Maia, Scyra7nathia, Latreillia, and 

 Homola, all of which are found within Indian limits 

 at 50-500 fathoms ; the lobster Nephrops andamanica, 

 found here at 1 50-400 fathoms, which differs only very 

 slightly from the Norway lobster (^Nephrops norvegica) ; 

 and the shrimps Pasiphcea and Crangon {Aegean) and 

 Pandalus, which are not uncommon here at similar 

 depths. Again, the order Schizopoda, which is almost 

 hyperborean in its proclivities, is represented in Indian 

 latitudes, at depths of 500-1750 fathoms by no less 

 than nine species. 



