Into the Depths 303 



This to some extent explains why we find many sim- 

 ilarities In the species of marine animals inhabiting the 

 regions at the opposite poles of the earth. Certain 

 families, genera, and even species have been observed 

 In both the Arctic and Antarctic seas, yet they seemed 



NEMATOCARCINUS; A DEEP-SEA CRUSTACEAN. 



to be entirely absent In the Intervening tropical zones. 

 But when the latter depths were dredged, some of those 

 forms were found; the low temperature of the deeper 

 water offered them a connection between the North 

 and South. 



In the deep sea Is found that very singular family of 



