246 University of California Publications in Zoology [Vol. 26 
forms in some regions, but there is nothing in the showing made by 
them which requires particular attention in this connection. 
The catches of 1920 (Allen, 1922) did not give any strong indi¬ 
cation that the species studied were peculiar to any particular section 
between San Diego and Puget Sound. It is therefore especially 
interesting to note that this more continuous series at a different 
season does give some evidence of restricted geographic range of 
some pelagic diatoms; e.g., the greater prominence of the genus 
Chaetoceras southerly, of Skeletonema medially, and of Thalassiosira 
northerly, and the possible difference in range of the two species of 
Asterionella, just mentioned. 
As to geographic difference in quantity production, there are some 
interesting points. In 1920, the largest individual catches were made 
in the regions near to or north of Cape Mendocino. In this series, 
the largest catches were made in the San Francisco region, consider¬ 
ably south of that point (table 1 and fig. 1). Furthermore, the aver¬ 
age production of catches in the San Francisco region is only slightly 
less than in the region of Destruction Island. On the other hand, 
only thirteen out of the sixty-five catches south of Cape Mendocino 
contained more than 10,000 to the liter while thirty-three of the fifty- 
four catches north of Cape Mendocino exceeded that number. Super¬ 
ficially, this seems to be strong indication that productivity is greater 
in higher latitudes. It is, however, one thing to say that higher 
latitudes are places of greater production and quite another thing to 
say that they cause greater production in the sea. For example, they 
may merely mark the region in which land drainage most favorably 
influences marine productivity. The showing in the San Francisco 
region makes it desirable to delay the statement of a conclusion until 
we are sure that latitude exerts a determining influence instead of 
merely accompanying such an influence. (Allen, 1922, p. 143.) 
Although it was not possible to make hydrographic observations to 
accompany this series of collections, records of temperatures at times 
of collecting were regularly made. These temperature records are 
partly summarized in the middle columns of table 1. As might be 
expected, this summary, shows a steady lowering of temperatures 
toward the north. Six out of eleven maximum catches were taken in 
temperatures slightly below the average for the region, but there is 
no special significance in this isolated fact. The fact that the two 
most consistently productive regions were those of lowest temperature 
while that of largest production was of a somewhat higher temperature 
