18 



HJALMAR BROCH. 



[REP. OF THE "MICHAEL SARS" NORTH 



Stalion 



10 



25 



51 



52 



56 



81 



82 



81 



86 



87 



88 



90 



92 



94 



Total 



Metres 

 0- 



2 



2 



2 



1 



4 



33 



18 

 10 



5 



1 



1 



92 



6 



4 

 3 



18 



19 

 6 



1 

 3 



1 



1 



-182 



- 13 



- 24 



- 15 



- 















1 







1 











- 2 



500- 















2 







2 



3 









- 7 



- 















1 











1 





1 



3 



1000- 















3 











2 





7 



- 12 



- 













2 



















- 2 



1500- 













3 



















- 3 



Table showing the distribution of the specimens of Pelagia perla in the hauls taken during the cruise of the 



"Michael Sars" 1910. 



The different rates of growth give the following result: 

 The larger the medusa, the smaller the manubrium in 

 relation to the mouth-arms. 



Do the proportions of the mouth-arms and the manu- 

 brium in these specimens differ from those in P. noctiluca 

 and P. panopyra, in other words: is P. perla specifically 

 distinct from the other two species? If this should really 

 be the case, the lines of correlation must lie differently 

 in the two other species than they do in P. perla, but we 

 cannot, at present, answer, this question, because the data 

 given by previous authors are in no way sufficient for such 

 investigations. The few measurements given by Bigelow 1 ) 

 are too scanty for an examination of the variations, and 

 Maas 2 ) merely states that the Indian specimens of his 

 collections have longer manubria than the Atlantic speci- 



mens, but says nothing about the size of the specimens 

 compared. 



The "Michael Sars" specimens are rather variable in 

 colour, some of them having a brownish or yellowish 

 tinted jelly, while the umbrella is mostly hyaline. In 

 the latter case the gastrovascular and genital organs are 

 throughout of a light bluish or reddish colour, the mouth- 

 arms being darker than the other parts owing to their 

 densely crowded and more vividly coloured nettle-warts. 

 The exumbrellar nettle-warts vary in colour from a dark 

 reddish brown to almost colourless. 



The colours are characteristic of a typical inhabitant 

 of the photic zone and the "Michael Sars" specimens 

 were taken mostly in the upper layers of water, as shown 

 in the table, the occasional specimens recorded from the 



') The Medusae (Rep. scient. res. eastern trop'cal Pacific "Albatross"— Mem. Mus. Comp. Zool. Vol. XXXIII) Cambridge U.S.A. 

 1909, p. 43. 



2 ) Meduses provenant des campagnes des yachts Hirondelle et Princesse-Alice, p. 57. 



