386 TRANSACTIONS OF THE [dEC. 13, 



from the 1,000 c.c. of water from each level is lodged in 20 e.e. 

 of the formalin preservative, while the above figures are taken 

 from the counting of 1 c.c. of such filtrate, or J^ part of the 

 whole litre of ocean water treated, at each level. 



It is not to be assumed, of course, that this reduces the analy- 

 sis of the contents of the water to a mathematical basis, as it only 

 furnishes ground for estimates, based upon actual counts ; but 

 we do believe that it gives a true picture of the vertical distribu- 

 tion of certain forms at the time the samples were taken. 



In notes taken in connection with the collections upon which 

 this paper is based, Harrington saj-s : " Tow taken in Port 

 Townsend Harbor varied greatly on successive evenings. It was 

 noticed after a rain that the surface water had a muddled ap- 

 pearance, and that the net was quickly clogged with a brown 

 coating of Goscinodiscus and Arachnodiscus, while on other 

 evenings comparativel}' few of these were to be seen. The num- 

 ber of medusoe varied very noticeably with the roughness of the- 

 sea, falling of rain, etc., and a strong inshore wind always brought 

 in A'arious organisms, such as masses of Noctiluca.^^ He also 

 states that the collection from which the plotting was made was 

 taken at the close of a week in which there had been hardly any 

 rain, and that in a glass jar the water was ver\' transparent, while 

 a few copepods could be seen in some of the samples. 



The causes for the sudden appearance of a given pelagic or- 

 ganism and its similar disappearance, in great numbers, are very 

 obscure, although the facts have often been observed. Whipple,* 

 from observations in the several basins of the water supply of 

 the city of Boston, Mass., has attempted to throw light upon the 

 seasonal increase in ceitain diatoms by assigning an causes the 

 vertical stirring up of the water, and the necessar}' presence of 

 oxygen in connection with the assimilation of nitrates by the 

 growing cells. Man}' interesting data have thus been brought 

 together by him, concerning the seasonal growth of this organism 

 in shallow fresh waters, but such conditions would with diffi- 

 culty be applied to marine forms over the much greater depths 

 here described, and it is probably true that there is more fluctua- 

 tion in shallow water and at the surface than in the deeper strata. 

 We also gather from the work of Professor John Walther,f 

 summarizing the work relating to the depth to which light pene- 

 trates, and its various spectrum absorption, etc., that the bottom 

 depths reached by our analj'sis in Puget Sound are onl}' about 

 half the distance to which the sun's rays can penetrate under 



*Some observations on the Growth of Diatoms in Surface Water, Technology Quar- 

 terly, Vol. VII., No. 3, 1894. 



fBionomie des Meeres, Jena, 1893, p. 35. 



