28 Sigurd Johnsen. 
Channel the same authors record two specimens of 65 and 73 mm. 
From the Norwegian Sea and the Norwegian coast are known 
the following specimens larger than 65 mm. (in addition to those 
recorded in the graph): Two specimens of 76 mm. from March 
and November; two undated specimens of 67 and 68 mm. 
It is always connected with a certain amount of uncertainty 
to base any conclusions on the negative data presented by the 
material of the expeditions that occasionally have investigated the 
life of the oceans. M. glaciale has, however, in the Mediterranean 
‘as in the Atlantic proved to be such a common species and the 
investigations have been carried out relatively frequent and in 
part with gear of such a great fishing capacity that the material 
hitherto known may, I think, be considered as giving in the main 
a correct representation of the species. There is no plausible 
cause for assuming that individuals, belonging to the group III, 
should be able to evade the fishing gears to a higher degree than 
the group II. The Irish, as well as the Norwegian investigations, 
have been carried out with bottomtrawl and pelagic trawl (young- 
fish trawl — midwater otter-trawl, “M. O. T” in the list of 
Holt & Byrne). When all the same the group III is wanting in 
the material of the Irish Atlantic slope but proportionately well — 
represented in the collections from Norwegian waters, this 
can not be due to a difference in the method of fishing but 
to a difference in the composition of the stock in these re- 
gions. The species thus must be supposed to attain 
alarger size in northern than in southern waters. 
This is very remarkable as the maximum size of a species generally 
is attained within its natural home and not at the outer boun- 
daries of its area of distribution. I think it can be explained in 
the following way. As shown on the foregoing pages M. glaciale 
seems to spawn only once in life, in the Mediterranean when 
1 year old in the Atlantic when 2 years old. The occurrence 
in the Norwegian Sea of still older (larger) specimens may be 
explained by assuming that maturity here is not attained before 
an age of 3 years, — a delay probably caused by the less favourable 
conditions of life in the northern waters (the lower temperatures). 
It would seem that the food-question is of no hindrance to the 
thriving of the species as shown by the size reached by the 
northern specimens; the small planktonic crustaceans occur in 
great quantities in boreal waters. 
