2 8 COPEPODA 



To deal with the vast topic of its seasonal occurrence in the area investigated by the Inter- 

 national Commission does not fall within the scope of this paper, and has fortunately been as well 

 done by Far ran as the in several respects incomplete material allowed. As, however, the important 

 contributions to the biology of Calanus finmarchicus by Dam as, Da mas & Koefoed and especially 

 by Paulsen are based upon material from the regions investigated by the Ingolf Exped., and as all 

 the conclusions, to which these authors have arrived, do not quite stand criticism in details, I feel 

 obliged to deal rather exhaustively with these papers. 



About the vertical distribution of the different stages it seems to be a general rule, that the 

 younger the stage of development the nearer the surface do the specimens live, as pointed out by 

 Damas, Paulsen and Far ran; the fullgrown females and males are generally spawning on the 

 surface in every case in the northern seas, as set forth by Damas & Koefoed, who write (1907 

 p. 393) "La ponte de Calanus finmarchicus s'opere visiblement a une profondeur d'autant plus grande 

 que la region considered est plus meridionale. Par la meme, la distance de la cote ou it se reproduit 

 augmente progressivement; autrement dit, cette espece prend un caractere oceanique de plus en plus 

 accentue." About the vertical distribution of the C. f. within the day I have only found observations 

 by Esterly, who writes (1911 pp. 140 — 151) as his conclusion: 



1) C. f. is most abundant at the surface about 7 — 8 p. m. during June and July. 



2) It has begun to leave the surface by midnight and is most abundant at a depth of 5—10 

 fathoms about midnight. 



3) The plurimum during the day (6 a. m. — 6 p. m.) is probably 200 feet. 



He thinks that the effect of light upon the "geotropisme of animals is probably the main factor 

 involved". On a much bigger material (1912, pp. 282—95) he arrives at almost the same result. 



Unfortunately he has not examined the part which the different stages play in these diurnal 

 migrations. 



My material was not well adapted for solving this question, but the difference in the number 

 of specimens taken by the Danish East Greenland Expedition in Denmark Strait ( 23_2 %) cf. tab. p. 21, 

 from North-East Iceland { 2 ~4/ 9 ), but especially from East Greenland (cf. tab. p. 26), indicate that all stages 

 inhabit the surface-layers in the night in some regions and at some seasons, in which only the 

 youngest Copepodites or the larves are frequent in the day. 



It must accordingly be admitted that there is a source of error in comparing the relative 

 proportion of the different stages contained in surface samples, as Paulsen has possibly done, as he 

 does not state whether the hauls are made in the day or in the night. 



It may perhaps be allowed to set forth one more general remark against Paulsens con- 

 clusions, that they are often based upon a too scanty material; even if, f. inst, five samples from a 

 certain region show almost the same proportion between the stages, it is not at all inprobable, that 

 the next 5 will show quite another result. 



Paulsen thus summarises (1906 p. 7) his results based on the Thors material from April 1904. 

 "In April, there are many adult Calanus finmarchicus and Nauplii at the surface of the sea to the south 

 of Iceland, many Nauplii (Sample 10) west of Iceland likewise on the surface. North of Iceland 

 there are but few adults and probably no juniorcs. Along the east coast of Iceland C. f. seems for 



