1914] Esterly: Ctenophora of the San Diego Region 27 



large individuals are not uncommon. For example, of the hauls in 

 table 1 numbers 2639 to 2762 were made in August, 1912. Out of a 

 random sample of 100 animals from haul 2747, only two were be- 

 tween five and seven millimeters in height, while the rest were from 

 one to four millimeters high ; there were two animals in the haul that 

 measured nine millimeters in height. Haul 2692 did not contain any 

 of the larger animals, the majority of the specimens being between 

 four and seven millimeters. The other August hauls are very similar 

 to 2747 and 2692. 



In hauls 3598-3637, on the other hand, which were made in Febru- 

 ary and April, 1913, the number of large animals was much greater. 

 For example, haul 3637 (April) contained fifteen animals between 

 twelve and fifteen millimeters high, but most of the specimens were 

 small, averaging from three to six millimeters. In haul 3606 (Febru- 

 ary) most of the animals were from ten to twelve millimeters, while 

 the smallest ones were not under seven. The three animals in 3604 

 (February) were ten, twelve and fourteen millimeters high. While 

 it is true that large hauls like 3606, 3608, and 3612 contain animals 

 from five to seven millimeters in height, the August hauls in the 

 warm region do not contain any that reach ten or twelve millimeters. 

 The nine hauls made in August in the colder water mentioned do, 

 however, contain the large animals in about the same proportion as 

 the February and April hauls. Of the six successful hauls in the 

 former group, only one was made in water above 18°, the other five 

 being between 16° and 18°. While the temperature of these hauls is 

 higher than that for most of the February and April hauls, it is true, 

 nevertheless, that the larger specimens of Pleurohrachia are found 

 only in water under 18°, as far as our investigations have gone. The 

 collections in February, March and April in the south and those in 

 the north (August only) alone contain Pleurobrachias that reach a 

 size of ten or twelve millimeters. I am unable to say what significance 

 this may have. There may be some meaning in the fact that the large 

 animals did not appear in our collections made in November and De- 

 cember when the colder temperatures prevail. Likewise, it may be 

 significant that no large animals have been taken in June and July, 

 although there are more than fifty hauls made in water of tempera- 

 tures at which they appeared in August around Santa Monica. A 

 discussion of the questions involved in the appearance of the large and 

 presumably adult specimens of PleurohracJiia at certain seasons and 

 under particular conditions would be subject to so much speculation 



