1911] Michael: Chactogttatha of tlic Sail Diego Region. 25 



plete without more apparatus. However, our explorations have 

 taught us much regarding methods of collection and apparatus 

 necessary for an adequate quantitative study of plankton dis- 

 tribution. We are convinced that direction and velocity of cur- 

 rents, temperature and salinity of M^ater, wind, clouds, fog, 

 rain, light, and darkness all affect the distribution of plankton 

 even ivithin a very small area. The influence of all these condi- 

 tions must be known to solve any problem concerning the 

 quantitative distribution of plankton. To increase our facilities 

 in meeting this requirement we have recently installed the Ekman 

 (1905a) reversing water bottles, the Nansen vertical closing net 

 (see Herdman, Scott, and Dakin, 1910, p. 275), Richter self- 

 registering deep sea thermometers (see Ekman. 1905a), and the 

 Ekman (1905b) current-meter that records the velocity and 

 direction of currents encountered in deep water. With this 

 apparatus we hope to discover relations in the horizontal and 

 vertical movements of plankton which will be valuable not only 

 to students of planktology, but to the commercial fisheries as 

 well. By strict attention to one locality we have obtained data 

 containing significant facts not present in the results of most 

 expeditions. Following the systematic part of this paper I have 

 discussed these data in so far as they concern the Chaetognatha. 

 I desire to express my obligation to Professor AVilliam E. 

 Ritter, Director of this station, and to Professor C. A. Kofoid 

 of the University of California for suggestions and advice con- 

 cerning the preparation of this paper. I am further indebted 

 to Dr. G. Herbert Fowler, Secretary of the Challenger Society, 

 to Dr. Hjalmar Broch of the Zoological Institute of the Univer- 

 sity of Christiana, to Dr. Rudolph von Ritter-Zahony of the 

 Royal Zoological ^Museum, Berlin, and to the Smithsonian In- 

 stitution for specimens of a number of rare and doubtful species. 



