162 U.S. NATIONAL MUSEUM BULLETIN 291 



Indian Central where productivity and food supply are lower. Also, 

 the bathy pelagic fish faunas of the productive subantarctic, subarctic, 

 transitional, and eastern equatorial regions exhibit a high degree of 

 endemism ; these faunas do not overlap into the sterile Central Water 

 masses. 



In his review of speciation of deep-sea fishes, Marshall (1963, p. 189) 

 concluded that 



earlier colonizers lived in more productive parts of the ocean : in those parts 

 most resembling the environments of their shallow-water ancestors, which were 

 probably fishes from subtropical and tropical regions. These more favorable parts 

 would be the waters over the upper reaches of the continental slope and those 

 in equatorial oceanic regions. The least productive parts of the tropical ocean, 

 particularly those underlying the great central gyres, would have been colonized 

 last. 



Concerning the colonization of temperate and polar waters, Marshall 

 (1963, p. 191) stated that the temperature barriers are less imposing 

 than the great contrast between growing and dormant seasons that 

 exist in higher, and particularly polar, latitudes. Bathypelagic species 

 that inhabit open ocean regions in the tropics must be adapted to the 

 uniformity and stability of continuous growing seasons; their meta- 

 bolic and reproductive rhythms would be unsuited to the unstable, 

 cyclic productivity of the high latitudes. But, great upwellings occur 

 along eastern boundaries of warm oceans, and the ". . . dominant 

 physical features of upwelling regions is their irregularity even under 

 normal conditions and this is paralleled with a constantly changing 

 biological picture" (Hart and Currie, 1960, p. 285). Therefore, the 

 productive, though fluctuating, conditions of upwelling regions offer 

 an environment somewhat similar to that of higher latitudes. Species 

 existing in upwelling regions may be preadapted to the fluctuating 

 conditions of temperate and cold waters; such species could be the 

 colonizers of the high-latitude waters (Marshall, 1963, p. 191). 



A more detailed analysis of the zoogeography of Bafhyteulhis in 

 the light of the preceding discussion must await more extensive ma- 

 terial from the Atlantic, Pacific, and Indian Oceans. The informa- 

 tion presently available, however, suggests that the physicx)chemical 

 and biological environmental conditions enumerated above (partic- 

 ularly organic production), acting as integrated isolating mecha- 

 nisms, have molded the distributional patterns exhibited by the popu- 

 lations of B. dbyssicola and B. hacidifera. If we assume that bathy- 

 pelagic cephalopods emerged and dispersed in a manner similar to 

 some other invertebrates and to deep-sea fishes, then the ancestors of 

 the species of Bathyteuthh could have arisen in the warm, produc- 

 tive seas, B. abyssicola has perhaps taken advantage of possible pre- 



