516 Peck u. Harrington, Plankton des Puget-Sound. 



The method of obtaining samples of water by means of a pump 

 through hose let down to the required depth was used by us in 1894 

 in Buzzards Bay to a depth of 20 fathoms, and the same method has 

 since been employed by Kofoid 1 ) with success in his shallow fresh- 

 water collections, and is recommended by Prof. Joh. Freuzel 2 ) as 

 an effective method, but we believe that for the small quantity of 

 water necessary for quantitative analysis by the S edg wick-Rafter 

 method 3 ) as here employed, or for the ,,planktonocrit" 4 ), the above 

 described apparatus is adequate and accurate for collections up to at 

 least 300 metres in depth. To a litre of the water thus obtained is 

 then added 20 cc of commercial formalin, by which the organisms 

 are killed after which the whole amount is filtered and then preserved 

 in 20 cc of a 5/ solution of formalin. Counting is then possible 

 according to the original Sedg wick-Rafter plan. 



In order to illustrate the distribution discovered through this 

 vertical in Puget Sound five representative subjects, both plant animal 

 and inorganic, were chosen from the data observed, and these have 

 been recorded by the plotting shown in Fig. 2 of this paper. The 

 most varied of these subjects is the diatoms, which have been somewhat 

 grouped together in this discussion in so far as they generally agree 

 in form and follow the same plan of distribution. Thus under the 

 generic title Coscinodiscus have been included in the plotting three 

 species typified by C. occulus iridis, while the larger sized forms of 

 the same general shape have been arranged under Coscinodiscus 

 asteromphalus, and include a few of the Genus Arachnodiscus, and 

 some individuals of Aulacodiscus. This plan seems advisable since 

 with the low magnification used in counting it is difficult to separate 

 the constituent parts with certainty, and they all show uniformity 

 throughout, which would tend to group them together in any synthetic 

 treatment. Under the genus Peridinium also are given two species. 



There are thus laid down on Fig. 2 five horizontal lines indica- 

 ting the five levels from which material was secured, and on these 

 lines were laid off distances corresponding to the numbers of individuals 

 of each group obtained by us ; the points were then connected by lines 

 and the enclosed areas shaded in black to indicate the living and 

 uumutilated condition of the organisms, and by oblique-lined areas to 

 show the certainly lifeless or fragmented individuals of the same 

 forms. The width of the black columns, therefore, at any of the ob- 

 served levels, indicates the proportionate abundance of the uumutilated 



1) Bulletin of Illinois State Lab. Nat. Hist, Vol. V, Art. I. 



2) Biolog. Centralbl., XVII. Bel., Nr. 5, S. 190. 



3) See Kofoid, ibid. p. 21, also Jackson and Whip pie in Technology 

 Quarterly, Vol. IX, Nr. 4, 1896. 



4) By C. S. Dolley, Proc. Acad. Nat. Sc. Philadelphia. Mai 1896. 



