CHAETOGNATHA COLLECTED BY STEAMER ALBATROSS. 275 



On the whole there is close agreement in number of teeth between 

 specimens of species common to the Philippines and the Siboga 

 region, while the same species are represented in the San Diego 

 region, if at all, by specimens having markedly fewer teeth. In 

 the face of this fact it is evident that, as formerly (1911, p. 68) 

 stated, "variation in number of both anterior and posterioi teeth 

 in many species is not referable to specific differences, but probably 

 to some distribution factor." When it is recalled that a subnormal 

 ocean temperature characterizes the region adjacent to the western 

 coast of America, due to pronounced upwelling of bottom water, 

 and that the chaetognath fauna off southern and Lower California 

 is representative of more northern latitudes, it suggests that one of 

 these distribution factors is temperature. I believe the small num- 

 ber of teeth in San Diego specimens is an expression of the slower 

 rate of metabolism due to a lower ocean temperature. This is not a 

 new suggestion, but it is one that merits thorough investigation. 

 Fowler (1906, p. 29), after stating that specimens of Siboga Sagitta 

 serratodentata have nearly twice as many posterior teeth as speci- 

 mens of the same length from the Bay o^f Biscay, says: "It is possible 

 that this may be correlated with the respective temperatures at 

 which the specimens live, but a long series of similar observations 

 from different latitudes would be necessary before this could be 

 regarded as even probable." 



LITERATURE CITED. 



AlDA, T. 



1897. The Chaetognatha of Misaki Harbor. Annot. Zool. Japon., vol. 1, pp. 



79-81, pi. 4. 

 BALDASSERONI, V. 



1915. Chetognati. Raccolte Planktoniche fatte dalla R. N. "Ligura" nel 



viaggio di circonnavigazione del 1903-05, vol. 2, pp. 85-117, pis. 6-7. 

 BERANECK, E. 



1895. Les Che"tognathes de la Bale d'Amboine. Rev. Suiese Zool., vol. 3, pp. 



137-159, pi. 4. 

 CLEVE, P. T. ; r 



1900. The seasonal distribution of Atlantic plankton organisms. Goteborg. 

 Vetensk. Vitterhets-Samhull. Handl. F., vol. 4, Heft 3, No. 3, 368 pp. 

 CONANT, F. S. 



1895. Description of two new chaetognaths. J. Hopkins Univ., Circ., vol. 14, 



pp. 77-78, pi. 1. 

 COSTA, A. 



1869. Di un nuovo genere di Chetognati. Ann. Mus. Zool. Univ. Napoli, vol. 5, 



pp. 54-57. 

 DONCASTER, L. 



1902. Chaetognatha, with a note on the variation and distribution of the group. 

 Fauna and Geogr. Maldive-Laccadive Archip., vol. 1, pp. 209-218, 

 pi. 13, figs. 39-40 in text. 

 ESTERLY, C. O. 



1914. A study of the occurrence and manner of distribution of the ctenophora of 

 the San Diego region. Univ. Calif. Publ. Zool., vol. 13, pp. 21-38. 



