MARINE BIOLOGICAL STATION AT PORT ERIN. nan 
There was also in the bay an autumn maximum, 
showing a very high peak at the end of September. 
Omitting, however, the single catch of September 30th 
(which is due in the main to Rhizosolenia semis pina), the 
peak is reduced to less than one-third its former height. 
A remarkable feature of this September hump was the 
sudden character of its appearance and disappearance and 
its short duration (six days). An inspection of the 
temperature curve of the year for the water of the bay 
shows that the sudden increase in the phytoplankton 
coincided with the maximum in temperature; and our 
weekly weather records at the Biological Station show at 
that same time a week of fine, calm weather with easterly 
breezes (S.H. and H.S.H.). I have noticed the same 
phenomenon in previous years, both at Port Erin and on 
the west coast of Scotland, which seems to indicate that 
if weather conditions be suitable at the end of autumn the 
phytoplankton may suddenly increase so as to constitute 
a second maximum in the year, the first being in spring; 
but that this possible “maximum” may be so modified 
in time and in amount by temperature and wind as to be 
unrecognisable. In 1906 it was very much more marked 
at Port Erin than in 1907, and lasted longer, while in 
1908 it was practically absent. 
The phytoplankton minimum for the bay occurs im 
August, no Diatoms being taken from August 9th to 
August 23rd (see fig. 17, above). © 
As an example of a sudden change in the plankton, 
we may compare the surface hauls taken in the bay on 
October Ist and 14th. The total quantities of the two 
gatherings were 1°5 and 11°5 respectively; on the Ist, 
Diatoms were relatively abundant (over 91,000); by the 
‘14th they had disappeared. But Sag/tta and various 
larvee, and especially Copepoda, had greatly increased in 
