CHAETOGNATHA COLLECTED BY STEAMER ALBATROSS. 271 



the most characteristic mesoplanktonic species in California waters. 

 Again, of those species common to both regions, Sagitta hexaptera and 

 S. serratodentata are second and eighth in order of abundance in the 

 Philippines and tenth and second in the San Diego region. Finally, 

 aside from S. neglecta, which is rare in the San Diego region and ob- 

 tained by only one haul from the Philippines, the order of abundance 

 of the remaining species common to both regions is as follows: S. 

 planktonis, P. draco, E. hamata, and K. subtilis in the Philippine 

 region; and E. limnata, K. subtilis, S. planktonis, and P. draco in the 

 San Diego region. 



Taken in connection with what is known of the distribution of 

 chaetognatha throughout the world, the above comparisons show that 

 the Philippine species are characteristic of the Tropics and warm 

 water, while those of the San Diego region are, on the other hand, 

 more characteristic of the Arctics or sub-Arctics and cold water. 

 As a matter of fact there is less difference between the California 

 chaetognatha and those of the region about Spitzbergen than there 

 is between the California and Philippine faunas. 



Furthermore, this sub-Arctic nature of the California chaetognatha 

 is not peculiar to that group. Calanus jinmarcMcus , the commonest 

 copepod of the California coast is, according to Cleve (1900, p. 47), 

 a " characteristic inhabitant of the Arctic regions, along the coast 

 banks of Greenland, Iceland, etc." Similarly, Eucalanus elongatus, 

 the second most typical copepod of California waters, is " noted from 

 60° north, 7° west in August and the Skagerak in February." [Cleve 

 (1900, p. 63.)] Likewise Acartia clausii, obtained in abundance off 

 the pier of the Scripps Institution, is typical of the North Sea "and 

 follows the coast of Norway to about 70° or 74° north." [Cleve (1900, 

 p. 42).] Again, the most prevalent ctenophore of the California 

 region, PleurobracMa bachei, "is found in vast swarms in the cold 

 water of Maine and Nova Scotia." [Esterly (1914, p. 28).] Lastly, 

 among the diatomaceae, Chaetoceros criophilum is the commonest 

 diatom in San Diego waters, although Cleve (1900, p. 295) states 

 that it is a "decidedly Arctic, pelagic species." Another common 

 San Diego Chaetoceros is C. debile, but Cleve (1900, p. 296) says that 

 it is abundant along the south coast of Iceland and at the Faroes." 

 Similarly with Nitzschia seriata, its "principal area of distribution 

 is between Scotland, Iceland, and Greenland" [Cleve (1900, p. 336)], 

 although it is among the common diatoms of the San Diego region. 



So the list might be continued. To be sure, there are many 

 tropical and semitropical species occurring in California waters, but 

 they are not the characteristic and prevalent ones. These have their 

 nearest allies, not in other parts of the world at corresponding lati- 

 tudes, but in the Arctic and sub-Arctic regions. May this not be 

 attributable in part to the marked upwelling of cold bottom waters 



