406 DEPARTMENT OF THE NAVAL SERVICE 



INTRODUCTION. 



By A. G. Huntsman, B.A., M.B., University of Toronto, Curator of the Atlantic 

 Biological Station, St. Andrews, N.B. 



In undertaking a study of certain groups of animals from the plankton, as pro- 

 posed by Dr. Johan Hjort, I have been obliged to limit it to certain forms that could 

 be identified with reasonable ease. Not having a special knowledge of these groups, it 

 has been necessary for me to repeatedly alter the scope and method of work during the 

 progress of the investigation. This has resulted in a lack of uniformity in the records 

 that would have been avoided if it had been possible to formulate a definite plan at tlie 

 beginning. 



This collection of plankton has been of the greatest interest, not only because it 

 came from localities representative of the greater part of our Atlantic waters and 

 permitted a survey of the whole region, but also because it came from waters of such 

 diverse nature. It has afforded an unequalled opportunity for an introduction to, if 

 not a solution of, the problem of the factors that are concerned in the distribution of 

 our planktonic species. The subject has been considered from that standpoint, namely, 

 to determine, if possible, the distribution, both vertical and horizontal, and the rela- 

 tive abundance, of each species. 



The time was too short for taking many closing-net hauls, which are so essential 

 in determining the vertical distribution. It was also unavoidable that the hauls were 

 not perfectly reliable for quantitative comparison of the regions covered. Some of the 

 factors to which this was due are: the well-known irregularity in the local distribu- 

 tion of species (their occurrence in streaks or shoals which may be taken or missed 

 in successive hauls at the same locality) ; the hauls not having been taken uniformly 

 either from the bottom, from a certain depth, or to the surface (at certain stations no 

 vertical hauls were made) ; the hauls not having been always strictly vertical owing 

 to the drifting of the ship before the wind; the variations in the coeflicient of filtration 

 of the net, depending upon its condition, the character of the plankton and the rate 

 of hauling; the individual factor, the hauls having been taken by different persons; 

 occasionally incomplete or faulty preservation; the difficulty in recognizing small 

 specimens in large quantities of plankton; the unsuitability of the method of capture 

 for large species (capturing too few) and for small species (their passage through or 

 retention in the net depending upon the other elements in the plankton). 



For these reasons the results as to distribution must be accepted with reserve and 

 considered as tentative merely. It has been necessary, however, to take the results as 

 they stand and, notwithstanding the large element of doubt, to put forth general views 

 which future investigation may either confirm or refute. Where possible, account has 

 been taken of these factors. Knowing the irregularities in the method of obtaining the 

 plankton, I have been frequently astonished at the apparent completeness of the 

 picture presented in the distribution of many of the species. 



The charts of distribution have been made graphic by lining in the supposed 

 areas of distribution, the positions of the stations from which data were obtained 

 being indicated by circles. This method is objectionable in that it shows perhaps more 

 than the facts warrant, but, since all the data are published, false impressions may be 

 corrected by reference to them. 



In some instances the hauls that were taken were not of the proper kind to show 

 definitely the presence or the absence of a species. Such stations have not been con- 

 sidered in plotting the charts, although many of them have been indicated on the 

 charts. For example, no vertical hauls were taken at Acadia Stations 10, 18-2'2, 27, 

 33, 43, 61, 77, and 90; the vertical hauls of the cruises of the Princess were not deep 



