HJALMAR BROCH. 



[REP. OF THE "MICHAEL SARS" NORTH 



taken at Stats. 53, 62 and 82, the diameter above the 

 furrow being respectively 11, 12, and 12 mm, but such 

 exceptions are rare. 



Depth 

 (meters) 



Stages 



of pigmer 



itation 



Total 



dodeca- 

 bostrycha 



inter- 

 mediate 



hyacin- 

 thina typ. 

















50 



5 



1 



— 



6 



100 



9 



— 



— 



9 



150—250 



5 



1 



2 



8 



500-600 



8 



23 



6 



37 



700—800 



5 



13 



3 



21 



1000—1100 



2 



11 



5 



18 



1250 



— 



4 



7 



11 



1500 



2 





10 



12 



Total 



36 



53 



33 



122 



Fig. 2. Table showing the bathymetrical distribution of 

 the three stages in pigmentation represented in the speci- 

 mens obtained by the "Michael Sars" in the North 

 Atlantic. The figures denote number of individuals. 



That the pigmentation, however, is correlated with 

 the bathymetrical occurrence of the specimens is clearly 

 shown by the accompanying table of vertical distribution. 

 The stages of pigmentation are placed in three groups, 

 viz. the slightly pigmented dodecabostrycha-gxoup, the 

 intermediate group, and the densely pigmented hyacin- 

 thina-group, and the rule is easily deduced that the darker 

 the specimens, the deeper they generally occur. 



The species has a bathymetrical range from a little 

 above 50 metres to about 1500 metres with a somewhat 

 prominent maximum about 500 metres. The faintly pig- 

 mented dodecabostrycha-'mdividua\s prefer the shallower 

 waters down to 500 metres, the dark-coloured, typical 

 hyacinthlna-'md'widuals predominate below 1000 meters, 

 while the intermediate group is found mostly in the 

 intermediate waters. 



Similarly we can generally trace an increase of size 

 towards the deep water, as might be expected from the 

 distribution of the different groups. In the accompanying 

 table the diameter of the bell just above the furrow where 

 the central disc attains its maximum diameter, is indicated, 

 and the figures denote the number of specimens of equal 

 dimensions at the different depths. Not only do we see 

 an increase in size towards the deeper water, but also 

 an increase in number, and it seems as if the largest 

 individuals occurred just below, where the greatest number 

 of individuals were caught, but on this point we must 

 acknowledge that the material is too scanty to allow us 

 to draw final conclusions. The smaller stages seem to 

 be missing in the deepest layers. How is this to be 

 explained in a species which is commonly supposed to 

 pass through a fixed bottom-stage? 



It is interesting to note that, in the "Michael Sars" 

 material, the apical projection of the stomach into the 

 mesogloea is mostly confined to larger specimens; in the 

 very smallest specimens there is no trace of a "Stielkanal". 



Finally we may consider the geographical distribution 

 of Periphylla hyacinthina (see fig. 4). The species is 

 widely distributed, having been taken in all oceans where 

 nets have been hauled in deep water. It has previously 

 been recorded from the Bay of Biscay, from the neigh- 

 bourhood of the Cape-Verde islands, from the Canaries, 

 from the continental edge east of the United States, from 

 Davis Strait, from south of Greenland, from many loca- 

 lities on the western coast of Norway, and also from the 

 Mediterranean. Thus it is not surprising that the "Michael 

 Sars" with its very effective fishing gear caught Periphylla 

 hyacinthina at most of the stations in the Atlantic, and 

 at Station 19 a little east of Gibraltar in the Mediterranean. 

 Further it must be noticed that to the west of the Mid- 

 Atlantic ridge the specimens were found in greater numbers 

 and at stations rather close together, whereas only a few 

 scattered specimens were caught between the Azores and 



Depth 

 (metres) 



Diameter of disc, above the furrow (millimetres) 



Total 



3-5 



6-10 



11-15 



16-20 



21-25 



26-30 



31-35 



36-40 



41-45 



46-50 



51-56 



56-60 



61-65 



66-70 



71-75 



76-80 



50 



1 



3 



2 





























6 



100 





5 



3 



1 



























9 



150-250 



— 



2 



3 



2 



1 

























8 



500-600 



4 



18 



8 



4 



— 



1 



— 



1 



— 



— 



— 



— 



— 



— 



— 



— 



36 



700—800 



1 



5 



7 



4 



— 



1 



1 





















19 



1000—1100 



2 



6 



2 



2 



3 1 



1 



















1 



18 



1250 



1 



3 



1 



1 



1 — 























7 



1500 



— 



— 



4 



3 



3 1 



1 





















12 



Total 



9 



42 



30 



17 



8 4 



3 



1 

















1 



115 



Fig. 3. Table showing the bathymetrical distribution and size of Periphylla hyacinthina. The figures denote number of individuals. 



