358 



TAGH SKO0SliKI{(; 



The plankton 

 investigntiona. 



This result is obviously definitely opposed to the view quoted above as being put forward 

 by C. Apstein, 1911, that Ph. (Ph.) ylobosa has a single planktonic copulation period limited 

 to the months of April, May and June. 



On account of this I carried out new investigations concerning this problem. In the first 

 place I investigated about a hundred plankton samples, taken during January, February, May 

 and July at Skager Rak and Cattegat by the investigation vessel ,,S k a g e r a k" for the 

 ,, Swedish Hydrographical Biological Commission". Secondly the plankton tables published 

 by the ,,Conseil permanent international pour I'exploration de la mer", on which C. APSTEIN' 

 had founded his view, were subjected to a renewed and careful investigation. 



The results of the first investigation seemed to support the view put forward by APSTEIN, 

 In all the samples from January, February and July this species was quite absent. Only in 

 a few samples from the month of May, consequently within the period suggested by APSTEIN, 

 did I succeed in finding it.' Both males and females were discovered. This is interesting because 

 the literature so far published does not clearly show whether both sexes are found swimming 

 freely in the higher layers of the water. The results are shown in the following table: 



The small number of females seems to indicate that the females return to the bottom 

 more rapidly than the males. 



The following are the residts of my re-examination of the plankton tables published by 

 the ,,C o n s e i 1 permanent": 



Philomedes (Ph.) glohosa is stated in these tables to have been caught at the following 

 stations on the following occasions: (The same terms are used in my work as those in these tables: 

 cc means very common, c common, + ., neither common nor rare", r rare, rr very rare, — means 

 that the species was not found). 



1903; May: Da 7, lat. oT" 52' N., long. 11" 18' E., depth to the bottom =: 87 m. 

 2. v., 1 ii 10 u. m. — 2 ii 20 a. m. 

 75 m. — 45 m. rr. 

 65 „ — „ + 

 10 „ — „ rr. 

 „ +. 



