Date of this Version
Published by the Proceedings of The American Microscopical Society, Vol. XVIL, 1895.
Only two methods of estimating the quantity of plankton obtained in a haul of the vertical net are known to me. These two may be called the volumetric and the gravimetric. Both have been used by observers in various parts of the world, but so far as I know have never been comparatively tested in order to ascertain the relative value of results obtained by the two. The experience of the past year has shown some disadvantages in the first method, while the second has certain evident objections which rendered its employment in this case out of the question. In the course of the work outlined in another paper (Ward 95) I worked out a modification of the volumetric method, or rather, perhaps, a way of combining the two methods so as to control and correct each other; this combined method is briefly outlined in the following, but for its better understanding a short account of the two previously existing methods is prefixed.