128 BULLETIN OF THE BUREAU OF FISHERIES 
has been done except from the Fisheries dock. This species appears to prefer the 
relatively impure water of bays and rivers, rarely being taken in coastal waters. 
Ctenophora present a very difficult problem to anyone attempting to determine 
seasonal distribution. They are found scattered throughout the year in many 
places. In this region the limits of the seasonal appearance are very definite, 
although the abundance varies greatly. Pleurobrachia pileus (figs. 27,28, and 31) 
Fic. 31.—Occurrence of Pleurobrachia pileus during successive years, 1893 to 1907 
appears in late December and remains until the latter part of May. The occur- 
rence during 1923 was very scattered. For a few weeks in December, 1922, they 
were abundant in all collections and then diminished gradually until February. 
From February until April few were seen, but on April 1 many appeared and 
remained throughout the month. In certain seasons immense swarms occur. 
During the latter part of April, 1895, Mr. Edwards often noted that the nets filled 
in a few minutes with these jelly-like organisms. 
