4. Contributions to our Knowledge of the Plankton of the 

 Faeroe Channel. No. IV. l Report on the Copepoda 

 collected by Dr. G. H. Fowler from H.M.S. ( Research' 

 in the Faeroe Channel in 1896 and 1897. By ISAAC 

 C.THOMPSON, F.L.S. (With an Appendix by Dr. FOWLER.) 



[Eeceived June 18, 1898.] 



The material upon which this Report is based was collected in 

 34 out of the 41 hauls (omitting 12 /, the depth of which was not 

 recorded). The Plankton had been immediately preserved in 

 formalin, corrosive sublimate, or picric acid, and kept in 5/ formalin 

 The Copepoda were picked out from the mass by Dr. Fowler, and 

 sent to me in bottles labelled with the number of the station and 

 letter of the haul whence the material was obtained. 



By means of messengers in 1897 and of a screw-propeller in 

 1896 (see pp. 570-575), the mid-water tow-nets were opened and 

 closed at will, enabling the depths to be almost accurately ascer- 

 tained, the limit of error being dependent upon the possibly impeded 

 rate of fall of the messenger or upon the accelerated rate of the 

 screw-propeller in a very heavy sea. 



The accompanying distribution table records the soundings, the 

 depths at which the various hauls were taken, the temperature (Fah- 

 renheit) at those depths, the number of meshes per inch of the net 

 used, and the occurrences of each species. It will be seen that all 

 the Copepoda collected are free swimmers, with one remarkable 

 exception, that of Aryulus, referred to later on. 



The collection furnishes some interesting facts as to the influence 

 of depth upon distribution. By far the commonest Copepod in the 

 collection, and probably the most widely distributed species known, 

 Calanusfinmarchicus, occurs abundantly in 32 out of the 34 hauls, 



1 For Part I. see P. Z. 8. 1896, p. 991 ; Part IT., P. Z. S. 1897, p. 523 ; 

 Part III., P.Z. S, 1897, p. 803. 



