1911] Michael: Chaetognatha of the San Diego Region. 77 



PART II. DISTRIBUTION 



EXPLANATION OF THE TABLES OF DISTRIBUTION 



The data from which the following discussions and con- 

 clusions have been derived are printed in full. It is believed 

 that, in connection with other plankton investigations, students 

 of this Marine Biological Station will find the data advantageous 

 for purposes of correlation. It is also probable that other 

 students of distribution, after accumulating observations, may 

 discover important relations suggested in these data. 



For convenience the data are arranged in four sections. 

 First, the surface catches are tabulated; second, those hauls 

 made with horizontal closing nets ; third, those made with verti- 

 cal closing nets, and fourth, those made with open vertical nets. 

 Temperature and salinity are not indicated in connection with 

 closing net hauls because, till the present, it has been impossible 

 to operate the water bottle and closing net at even approximately 

 the same time. For records of relation between depth, tempera- 

 ture, and salinity see McEwen (1910). Temperature is recorded 

 in Centigrade, depth in fathoms, and latitude and longitude 

 to one-tenth of one minute measured from Greenwich. 



The following symbols are employed to indicate the various 

 nets used in making collections : 



A. Surface net 000 XX mesh silk bolting cloth, orifice 



97.5 cm. in diameter. 



B. Kofoid closing net 000 XX mesh silk bolting cloth, 



orifice 37.0 cm. in diameter. 



C. Nansen closing net 1 XX mesh silk bolting cloth, 



orifice 109.5 cm. in diameter. 



F. Nansen closing net 000 XX mesh silk bolting cloth, 

 orifice 45.2 cm. in diameter. 



Method of Counting 



If a haul seemed to contain under three hundred individuals 

 of a species they were counted. When the number appeared 



