THE PLANKTON IN ST, ANDREWS BAY 3 



SESSIONAL PAPER No. 39b 



genus. They calculated that there would be, at a minimum, twenty million 

 Peridinia in a single fish. 



The truth seems to be that all methodical observation has an experimental 

 basis, and the merit of advancing biology to the rank of an experimental science 

 does not rest entirely with the mechanists of the present decade, nor even with 

 the hybridists, great as have been the results of their respective labours. 



With reference to the constitution of the Plankton, Haeckel (Plankton-Studien, 

 1890, p. 66) insisted upon the fact, known to every experienced planktologist, that the 

 first and most striking peculiarity is the variable combination of its component units. 

 The differences of composition are both qualitative and quantitative and are as 

 noteworthy when comparing different localities at the same time, as when com- 

 paring different seasons at one and the same station.* Under these circumstances, 

 in order to secure complete and reliable data respecting the periodical fluctuations 

 of the Plankton, it is necessary to institute continuous series of observations at a 

 given locality throughout at least one entire year, and better still through 

 several successive years, after the manner adopted in recording meteorological 

 conditions, with which the various planktological conditions are directly and 

 intimately correlated. 



In illustration of the kind of data concerning the circulation of Plankton in 

 coastwise currents, which may be obtained by the co-ordination of observations 

 made at different stations at the same season or at different seasons, I may mention 

 that a certain small Crustacean species, named Acartia clausi, was the most abun- 

 dant representative of its order (the Copepoda) at St. Andrew's in July and August 

 1912. It was not found at Woods Hole, Mass. during the same two months in 

 1899 (W. M. Wheeler) ; but it occurred abundantly in Naragansett Bay in January 

 and February 1906 (L. W. Williams). 



This species belongs to a section of Copepoda termed Calanoida by G. 0. 

 Sars, the veteran author of "An Account of the Crustacea of Norway," one of the 

 standard works of reference on this subject. The Copepoda of this group afford 

 nutriment to several common food-fishes. Calanus finmarchicus, a relatively 

 large species attaining a length of four millimetres and a leading type of the North 

 Atlantic zooplankton,f is known to be the food of the herring along the Nor- 

 wegian coasts. Very few examples appeared in my tow at St. Andrew's, and 

 these were immature, not exceeding three millimetres in length. If it should 

 ever be found in quantity within the bay of St. Andrew's, it would make a notable 

 record. Arctic specimens of C. finmarchicus attain a maximum length of five 

 millimetres (G. 0. Sars). 



Associated in the tow with the Calanus, and not so rare as the latter, was a 

 transparent, fragile being belonging to the group called Tunicata-Appendicularise, 

 named Fritillaria borealis. This little creature is shaped like a miniature hammer, 



* On this point attention should be drawn to Professor Herdman's Plankton Investigations 

 in the Irish Sea. Vide 26th Ann. Rep. Liverpool Mar. Biol. Committee. December 1912, p. 36. 

 Also Prof ssor Mcintosh's Planktoi Reports, Scot. Fish. Bd. R'p , 1890, etc., and Dr. William- 

 son, Plankt n Reports, Scot. Fish. Bd. Rep., 189S, etc. 



f Animal plankton as distinguished from Phytoplankton comprising the pelagic Algae. 



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