166 Part L11.—Sixteenth Annual Report 
shows that their movements are more or less erratic. On February 14, 
1890, Euphausiide are recorded as ‘‘common” in a bottom tow-net 
gathering at Station V., but at Station VII., a little to the south of 
Station V., trawled the previous day, they are described as “ very rare,” 
while, on the other hand, the Mysidse weré more common, and in much 
greater variety, at this station. Moreover, at Station I., which is in line 
with Station V., but a little farther west, and also at Stations IL., IIL, 
and IV., which were all tow-netted within a few days of each other, 
Kuphausiide are either altogether absent from the tow-net lists or they 
are described as “rare.” These Schizopods were again present in the 
Forth in considerable numbers in the following March; they were 
common at Stations I., IIL, IV., VIII, and IX., but few or rare at 
Stations II., V., VI, and VII. During the following summer 
Euphausiide were entirely absent from, or were very scarce in, the 
tow-net gatherings which were then collected; but the records for the 
ensuing month of October describe these organisms as frequent at some 
of the stations during that month, and they continue to be represented 
in the tow-net gatherings in varying numbers, from one or other of the 
stations, all through the winter and on to the spring of 1891. During 
the summer and winter months of that year comparatively few records of 
the Kuphausiide occur in the lists of tow-net gatherings, and not till the 
beginning of 1892 is there much increase in the number of the records ; 
but, though in February and March there is a decided increase, the 
captures of them even then are usually described as “few” or “rare.” 
With one or two exceptions, Schizopods continued to be scarce in the 
tow-net gatherings till the winter of 1893-94, when they appear to have 
become more than usually numerous, and, in a considerable proportion of 
the gatherings collected during December and January of that winter, 
they are referred to as ‘‘common” or “ frequent.” With the advent of 
summer, however, and from that time on into 1895, the numbers of these 
crustaceans are again considerably reduced. From a study of all the 
facts at our disposal in the published records in the Fishery Board’s 
Annual Reports for 1889 to 1896, there seems to be a fair amount of 
evidence tending to show the existence of a more or less regular yearly 
increase and decrease in the numbers of Schizopoda present in the estuary 
of the Forth, but the reason of this increase and decrease is not sufficiently 
clear to permit at present of a satisfactory explanation. 
Besides this apparent yearly variation referred to, there also appears 
to be a fluctuation, which may or may not be regular, that extends over 
a longer time. I refer to the presence of Schizopoda in considerable 
numbers in the winter of 1889-90, and again in the winter of 1893-94 ; 
but to ascertain whether this variation is merely accidental or not would 
have required the investigations to be carried on over a much longer 
period than they have been. In considering this question of the seasonal 
variations of the Schizopoda, J have dealt mainly with the Euphausiide, 
because this family is the one most numerously represented in the Firth 
of Forth, and the one which has shown the greatest tendency to a regular 
periodic increase and decrease. The Myside, also, to some extent show a 
similar tendency to variation, but the variation is scarcely so well marked 
as in the case of Euphausiide. 
