188 Part III.—Sixteenth Annual Report 
each of the three outer stations are those for May and August; while at 
Station IV. the highest is that for May, and at Station III. for June; but at 
Station I. the highest is that for February. The next highest numbers 
are those for April, May, and August. Some of these points are more 
clearly indicated by the three formule. 
Formula (1) shows, as before, the total number of records of Acartia 
for each of the stations :— 
(a) Inner Stations. (b) Outer Stations. 
Numbers of the Stations, = Oe Hee Va V. Villy ie 
Total number of Records for each Station, 23 26 28 25 TBs 21 
The station with the lowest number is [X., while that with the highest 
number is IV., the difference between them being seven. 
Formula (2) shows the total number of records of Acartia for each of 
the twelve months for the seven years, (a) for the inner stations, L., IIL, 
and IV.; (6) for the outer stations, V., VIIL., and IX. ; (c) for all the 
six stations :— 
Names of the Months, ad aE Be z 2 b . = 5 2 
Se@ade5ntnoaga 
(az) the Inner Stations, 0 9° 2 11 Tt F610 Are 
ares (b) the Outer Stations, Oe 2 718 - ee 2 be ¥ a 
Month, for ( (c) all the Six Stations, - 014 418 24161025 91212 2 
If these figures be closely examined and compared, it will be found that — 
there is a more or less evident maximum in the total number of records 
about every three months. This is also found to be the case, though not 
so distinctly, when the numbers are divided so as to correspond with the 
inner and outer stations. But taking the total numbers first, it will be 
observed that, commencing with February, the total number for which is 
fourteen, there occurs in March a sudden drop, after which the numbers 
increase till May, when the second highest total for the whole year is 
reached. In June and July the numbers again fall, to be followed by a 
marked accession 1n August, so much so that the maximum for all the 
twelve months occurs then; in September there is again a marked 
decrease, after which a slight recovery takes place in October and Novem- 
ber, while in December the number is, next to January, the lowest for 
the year. This increase and decrease, though not so apparent where the 
numbers are divided to correspond with the inner and outer stations, can 
still be traced, especially in the series corresponding to the outer stations. 
The reason for this apparent rhythmical arrangement is not very clear, 
and it may be that the seemingly periodic recurrence of Acartia may be 
“merely accidental. 
Formula (3) shows the total number of records of Acartia for each 
year, for (a) the inner stations, I., III., and IV.; (0) the outer stations, V., 
VILJ., and IX. ; and (c) all the six stations :— 
Numbers of the Years, : - = 1889, 1890. 1891. 1892. 1893. 1894. 1895. 
(a } the Inner Stations, - 4 10 24 16 14 5 4 
otal pombe (3) the Outer Statios,- 4 13 2% 18 5 4 5 
Year, (c) all the Six Stations,- 8 23 49 (99. 19. Ouaag 
It wili be observed that the maximum number—that for 1891—is pro- 
portionally considerably greater in comparison with the others than is 
observed either in the case of Calanus or Temora. 
A few of the other species of Copepoda referred to in the lists of tow- 
net invertebrates, such as Pseudocalanus elongatus, Centropagus sp., 
Anomalocera patersont, aud O2thona sj., are also’ at times more or less 
freyuent in the Firth of Forth, but the published records of them show 
that they are usually less common than those already noticed. 
