No. 553] DISTRIBUTION OF THE CHJETO GNA THA 29 



C. to 5°. 3 C. It is reported from both epi- and meso- 

 plankton of the north temperate and tropical Atlantic and 

 tropical Indo-Australian oceans, as well as from the epi- 

 plankton of the south temperate Atlantic and south tem- 

 perate Indo-Australian oceans and from the mesoplank- 

 ton of the north temperate Pacific. K. pacifica, on the 

 other hand, is a warm-water epiplanktonic species from 

 the tropical Atlantic and Indo-Australian, and the north 

 temperate Pacific oceans. Its northern limit is 35° N. 

 and its southern 7° 30' S. During the Siboga expedition 

 both species were taken together in but one haul, and that 

 one made by an open vertical net from 1,000 fathoms. 

 This is the only instance, so far as I can ascertain, where 

 both species have been obtained from the same area. 



In summing up we find that the members of each "coup- 

 let ' ' tend to be isolated in one way or another. 8. neglecta, 

 for instance, maintains a distribution which, while over- 

 lapping more or less, is contiguous rather than coin- 

 cident with that of 8. regularis. In the case of S. bipunc- 

 tata and 8. decipiens the data show that wherever both 

 are taken within the same area the former is confined to 

 the epiplankton, while the latter occurs only in the meso- 

 plankton. With S. lyra and S. gazellce the distribution is 

 never coincident, but, in some instances, contiguous and 

 overlapping. 8. enflata and 8. hexaptera present the 

 most striking evidence in favor of coincidence but, even 

 here, the chances are that only the immature of S. 

 hexaptera occur in the upper epiplankton, so that an 

 effective physiological isolation is probably maintained. 

 S. planktonis and 8. ferox, while they do occur together 

 in the Siboga area, are isolated by their manner of ver- 

 tical distribution, 8. ferox being epiplanktonic and S. 

 planktonis mesoplanktonic. The members of the doubtful 

 "couplet" comprising E. ham at a and E. fowleri are only 

 rarely taken in the same net hauls, which indicates con- 

 tiguous rather than coincident distribution, although this 

 appearance may be due entirely to the fact that E. fowleri 

 is not abundant anywhere. Finally, K. subtilis and K. 



