294 University of California Publications in Zoology [Vou.9 
In table 19 the greatest averages per hour (column 6) are 
at the highest densities in two cases out of four (line 3, sections 
A and B). In other words, the animals are most abundant 
during brightest daylight (8 am — 4 p.m.) and early morning 
(4 am—8 a.m.) at a salinity of 33.649 or more. But they are 
most abundant and most frequent during twilight hauling 
when the salinity is lowest (section C, line 1), and during. late 
night (section D, line 2) at a salinity of 33.605-33.648. It 
seems to me that such an erratic distribution of abundance in 
respect to salinity can only mean that that factor is negligible 
in the determination of distribution. Michael (1911, p. 139) 
found that Sagitta bipunctata is always most frequent and 
abundant at salinities between 33.605 and 33.648. There is 
no reason to expect that such a relation between abundance 
and salinity, in regard to consistent results at least, should be 
absent in the case of Calanus if salinity is a factor in distribu- 
tion. It is of course possible that a relation between abundance 
and salinity would be established if a larger number of hauls 
were available, but as far as our data go at present we are 
hardly justified in claiming that there is such a relation. The 
animals are known to be mostly a long distance below the 
surface from 8 a.m. to 4 p.m., and the relation between abund- 
ance and salinity during these hours (as shown in table 19, 
section B), concerns a relatively small proportion of the popula- 
tion. When they are most abundant at the surface (4 p.m— 
4 am.) the abundance is greatest at this salinity at one time 
and at that at another (table 19, sections C and D). On the 
whole, we are not warranted at present in forming a definite 
conclusion as to the effect of salinity on distribution. 
Farran (1910, p. 83) has recently summarized the facts 
as to the distribution of Calanus finmarchicus, including under 
that name the species known as helgolandicus and septentrionalis. 
The form is designated as eurythermal and stenohaline, the 
temperature limits (p. 87) being from 16° at the surface to 13° 
at the bottom in the mouth of the English Channel; in the 
north it is found in waters of 0° or less. Cleve gives the 
temperature limits in the North Atlantic as 22°C to 0°2C. 
(Farran 1910, p. 87). Farran states (p. 88) that the organisms 
