No field of research is more inviting to the student of science than the one offered by the waters teeming with minute animal and plant life. Work in this interesting line of investigation has progressed slowly because of a want of adequate collecting apparatus, which, until quite recently, has been limited to two simple types, the net working vertically through the water and the one working horizontally or obliquely, both of which present serious disadvantages, prominent among which is the liability to damage and loss. These nets are of necessity made of very delicate fabric and must be operated in water where there are many obstacles to tear and destroy them. The finer qualities of bolting cloth, of which the better nets are made, cost from $6 to $8 per yard. To spend this amount for material, a day or two in constructing the net, and then in the first haul to catch a huge snag that destroys the net is neither a delightful nor an uncommon experience.
   Secondly, it is impossible to determine with any degree of accuracy the volume of organisms actually present in a given quantity of water. This difficulty arises from two causes: First, the manipulation of the net is attended with such disturbance as frightens away many of the organisms; secondly, it is impossible with the net to measure the water filtered. It is evident that if we wish to ascertain the number of crustacea, for instance, that exist in a cubic foot of a certain water, we must first be able to get a cubic foot of the water; with the net we cannot do this, for even though we know the area of the net opening it is so constructed and operated as to push aside some of the water, so that the net does not filter the entire column of water through which

it passes. Thirdly, the plankton is unequally distributed in the various vertical zones or strata of the water; for instance, certain groups are characteristic of the surface stratum, others of the bottom atratum, and still others of the various intermediate strata. The determination of the various groups characteristic of these different strata constitutes one of the most important features of the collector's efforts. It is evident that with the net we cannot collect the plankton of one stratum without mixing it with others. Fourth, ice precludes the use of the net during the winter months, which, in fact. represent the best season for plankton work.
   These, together with other difficulties, have led students to seek other means of collecting. Among other forms of apparatus in recent use is the plankton pump. a machine very similar to the force pump. While the pumping method cannot be said to eliminate all the disadvantages mentioned, yet we may say that it reduces these difficulties to a minimum. The. writer determined last fall to attempt the construction of it light plankton pump that might be carried about and operated by one person; a simple plan of construction was suggested by Dr. H. B. Ward. This plan, with some modifications, finds embodiment in the pump its it now stands.*
   The instrument is practically a force-pump, whose form and mode of operation are indicated in the accompanying plates. The cylinder of the pump is 11x 3 1/2 inches and has a capacity of 347 1/2 cubic inches per stroke. The stroke of the piston is definite in length and is regulated by a lock-nut as shown in the plate.The valves used are finely ground check-valves, to which, it is believed, the accuracy of the working of the apparatus is largely due. The pump is connected with the water by a hose 1 1/2 inches in diameter, whose lower end is adjusted to the various vertical zones of water by means of attachment to a floating block.
   The net was constructed primarily for collecting crustacea. It consists of a tin cylinder (g, Fig. 9) 6x6 inches, to which is

soldered a truncated cone; to the lower end of the conical part is attached the filtering apparatus (h), which is a cylinder 4 x1 1/2 inches, made of fine wire gauze containing eighty-three meshes to the linear inch. The upper portion of the tin cylinder has fitted to it a detachable rim, by means of which a net cover may be attached to the apparatus for the purpose of preventing

FIGURE 8.--Sectional view of the pump, showing direction of the current as the piston rises.

the entrance of objectionable matter. To the rim mentioned are attached the supports (f) as shown in the figure. The filtering apparatus is so constructed that a net of bolting cloth may be attached outside of the gauze filter, thus adapting the instrument (which may be used separately) for the various work

of the ordinary net. Most gratifying results have attended the use of this pumping apparatus during the last few weeks. It is possible with it to measure with almost absolute accuracy the amount of water filtered. The average amount of water thrown at each stroke is 347 1/2 cubic inches. Careful tests show that the greatest variation above this average is 1.9%, and below only 1.3%, thus making the extremes between the least and the greatest amount thrown but 3.2%. The collecting can be carried an without any disturbance to the water, and the water can be drawn from any stratum, thus enabling one to get the vertical distribution of the plankton.
   Material has been collected from the midst of debris and also during the winter months when the water was covered by a thick coat of ice.

EXPLANATION OF FIGURE 9.

   c, Cylinder of pump; e, handle of piston rod; d, lock-nut; b, check valves; k, attachment of hose;
i, distal end of hose; g, cylinder of net; h, filtering apparatus; f, support.

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