206 Influence of Temperature on the Depth of Marine Species. 
The great care and thoronghness of Prof. Forbes’s researches, 
and those also of MacAndrew, give peculiar weight to the conclu- 
sions. Those species are taken from the tables which are com- 
mon to these several regions, and with regard to which the ob- 
servations are free from doubt ; and we have confined the list to 
the Acephalous Molluscs; as these appear to be sufficient to test 
the law under discussion. The depth is given in fathoms, — 
It should be observed, that, to carry out the theory, the species 
should be confined to shallower waters to the north than to the 
south. 
To compare fairly this table, it should be noted that the dredg- 
ing at the Shetlands, Orkneys, and north of Scotland, was carried 
to a greater depth than about southern England, fifty fathoms 
being the limit in the latter region, as the waters are shallow, 
Making this allowance, we are still struck with the great depth 
to which the species penetrate at the most northern locality, 
instead of the small depth. Out of the 21 species which are 
mentioned as oceurring in northern Scotland or the Shetlands, 
and the Aigean, 14 or 15 descend to a greater depth in the for 
mer than in the latter ; and nearly all the species common to the 
north and south extremities of the British Islands, are reported 
from the deepest waters at the north. Of the observatious made 
at Vigo Bay, Malta, Pantellaria, Tunis, Algiers and Gibraltar, 
there is but a single example among the above species of a greal- 
er range in depth than occurs in the northernmost locality exam 
ined. The dredging in the Mediterranean by McAndrew, oh 
not carried to as great depths; yet even allowing for this, the 
facts are not a little remarkable. 
, Yow the temperature in the Aigean during the warmer months, 
according to Lieut. Spratt, is as follows, At the surface 76° too" 
. 10 fathoms, seldom below 74° in the summer. 
20 6s rT “ 68° « a 
35 3 ts 3 62 4 Ht ® 
75 “ 5G « &é sf 
100 to 300 « we “« 55 to 554°... 
The temperature of the waters near Southern England 
summer is 62°; and near the Shetlands 55° or less. ce | 
quently the surface summer temperature of the British Channe 
is not found in the Augean at a less depth than 35 fathoms, * 
the surface summer temperature of the Shetland’s is the tem 
ature at one to three hundred fathoms in the Aigean ; aud ot 
species that range to a depth of 100 fathoms about northern yar 
land are found within 30 fathoms of the surface in the gea™, ° ts 
is where the summer temperature is 74° or more. Such fae" 
show the hardiness of the Species in enduring great ranges wowed 
perature. We must therefore conclude that it is not te™ 
