796 Proceedings of Royal Society of Edinburgh. [ SEss. 
to indicate a difference in the seasonal distribution of the species of 
Podon. 
(3) The Isopoda. 
Hurydice achata, Da Costa.—A single specimen of this Isopod 
was obtained in a plankton sample collected near the Marine 
Station on 24th April. This species, which is not uncommon in 
some parts of the Clyde estuary, is an active swimmer, and this 
may account to some extent for its absence in these gatherings. 
(4) The Amphipoda. 
Gammarus locusta (Lin.) was the only Amphipod observed, and 
it occurred in three of the earlier gatherings; it is a demersal 
species, and therefore its presence even in these three may have 
been accidental. 
(5) Larval and other Young Forms. 
Young Balani, especially in the Cypris stage, were moderately 
common in the samples collected in April, and they occurred, 
though only at intervals, up till the end of May, but after that 
time no more were observed. 
Other young Crustacea, representing various groups, as the 
Brachyura, Macrura, Carida, Schizopoda, etc., were observed at 
more or less regular intervals throughout the summer, sometimes 
sparingly and at other times moderately common. They were 
present in all the samples collected from about the middle of May 
till the first week in June, but both before and after that time 
they were only occasionally observed. 
It will be observed, from the remarks on the various species and 
also from the table (Table I.), that four of the Copepods have a 
distribution more or less continuous throughout the six months 
during which the collection was made; there is an apparent 
increase and decrease in the numbers of individuals captured 
belonging to each species, which may possibly be due to seasonal 
variation ; this variation is, however, rather more marked in one or 
two of the species whose distribution is not so continuous as those 
specially referred to, as, for example, in Zemora longicornis. 
