80 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
downs to their maximum on April 5th, and then 
decreased until their disappearance on April 26th. None 
were taken at any other time of the vear. The ‘“ Cypris ” 
stage follows on after the Nauplius. It was first taken in 
the bay on April 6th, rose to its maximum on the same day 
with ‘the Naupli, and was last caught on May 24th. 
Throughout, the ‘“ Cypris’”’ curve keeps below that of the 
Nauplius, the maxima being 1,740 and 10,500  respec- 
tively. Probably the difference between the two curves 
represents the death-rate of the Balani during the 
Nauplius stage. The curve for 1908 seems to be much 
the same. 
The two large Copepoda Calanus helgolandicus, Claus, 
and Anomalocera pattersoni, Temp., are both regarded as 
“oceanic ”’ species, and are both present in fair abundance 
in the Irish Sea. ‘They are two of the most conspicuous 
objects in our plankton gatherings, and can readily be 
picked out with the eye and counted. 
Calanus was present in our gatherings in 1907 during 
every month of the year from January 8th to December 
30th. It was represented on nearly every occasion when 
hauls were taken, and in some cases when absent from one 
net it was taken in another gathering made on the same 
day, showing that the apparent absence was due either 
to irregular distribution or to some imperfection in the 
sampling of the sea. When, then, we find that a species 
like this is not recorded from a particular haul at a time 
of year when gatherings are being taken once a week 
only, one is inclined to suspect, from the appearance of 
the records at other times when the observations were 
more frequent, that if another haul had been taken that 
day or on an adjoining day the missing species would 
have been represented. Negative evidence must always 
be received with some caution, 
