STOCKHOLM, 1899. Ill 



undertaken by the German Seefischereiverein in the North Sea in the 

 beginning of 1895, and minutely described by Hensen and Apstein. 



The method employed is as follows : A funnel-shaped net with a ring 

 1| metre in diameter, and capable of folding or closing up, and with a 

 bag, to the end of which a beaker is attached, is let down perpendicularly 

 to the bottom and then drawn up, until it hangs at the side of the ship. 

 The net is then rinsed with a jet of water, so that its entire contents 

 are washed down into the beaker at its extremity ; the beaker is then 

 detached and its contents removed. 



It is usually impossible to examine this material at once, and it must 

 consequently be suitably preserved for study ashore. The method of 

 preservation should likewise be identical throughout the whole series of 

 researches, as also should be the size and mesh of the net. The net is 

 constructed of miller's gauze (or "bolting-cloth"). No. 3, as already 

 used in the German deep-sea expeditions. 



4. The ship has to be laid on a determined course, and an observation 

 taken at least every twenty knots. If at the first glance eggs are pre- 

 sent in considerable numbers in the catch (in which case over 200 eggs 

 will be present), it will be necessary to take samples at shorter intervals, 

 according to the judgment of the person in charge. 



5. The eggs so obtained must be examined on shore for the purpose 

 of estimating their number, and, so far as possible, of determining their 

 species. 



Specific determination of the larvte, and even of the embryos in the 

 eggs, is admittedly possible, and for such determination the works of 

 M'lntosh, of Apstein, and the forthcoming publications of the Heligo- 

 land station, will afford material. The young eggs of the plaice, sole, 

 etc., can be identified and therefore enumerated, while the eggs of the 

 cod and haddock in the early stages of their development cannot, with 

 our present knowledge, be distinguished from each other. 



6. It is to be supposed that the hydrographic cruises in February, 

 May, August, and November will also furnish material for determining 

 the occurrence of e^RS and larvse, and will indicate when the time is 

 come, or is approaching, for the commencement of systematic observa- 

 tion of the eggs. Since the spawning period differs somewhat in different 

 years and in different parts of the sea, an agreement as to new courses 

 of investigation in special areas of the various seas must be arranged 

 through the central bureau or otherwise, on the basis of the results 

 obtained during the hydrographic and other cruises. 



7. Other methods for the numerical estimation of eggs and larvse are 

 by no means to be excluded, but should not interfere with or supplant 

 the methods of research determined by international agreement. 



Hensen. 



