486 GEOLOGICAL SURVEY OF THE TERRITORIES. 
other species of crustaceans examined by me, we can observe all these 
modifications of the influence of the surroundings upon the organism. 
The formation and full development of the gill-sacs and posterior 
branchial lobes depend in Artemia and Branchipus not only on the 
salt-quantity of the water, but also on its temperature; since by a low- 
ering of temperature the size of the gill-sacs decreases, by a heightening 
of the temperature they enlarge. Ido not possess sufficient measure- 
ments concerning the posterier branchial lobes by which I could attest 
with correct figures the change of these appendages by temperature, 
although I obtained unmistakeable results, according to which they, 
contrary to the gill-sacs, but in a less degree, enlarge by lowering the 
temperature. Putting temporarily the posterior branchial lobes aside, 
I shall treat of the gill-saes only. 
In measuring the gill-sacs in specimens of Artemia salina, gathered 
in the first half of September out of the Chadschibai Lake, I was sur- 
prised at the figures obtained by the relation of their size to the length 
of the body, deviating far from the figures received in measuring the 
summer-forms, although the density of the salt water in the lake was but 
little lessened. Later in the fall, the specimens of Art. salina collected 
out of the Kujalniker Lake, at a density of the salt water of 139 Beaumé, 
had even a little smaller gill-sacs than the specimens collected in sum- 
mer at 9° Beaumé, from the Chadschibai Lake. Subsequently, I di- 
vided the young and old specimens taken from the Kujalniker Lake 
at a density of 13° Beaumué into two sections and domesticated one 
section at an average temperature of 14° [Réaumur?] the other section 
at an average of temperature of 7°+ Réaumur. A considerable differ- 
ence showed itself after two weeks, those individuals living at a lower 
temperature, but kept by me at a uniform concentration in both jars, 
had their gill-saes, especially in width, considerably smaller. In indi- 
viduals Jiving in higher temperature, each gill-sac on the eighth pair of 
legs on the average amounted to the twenty-second part in length and 
the forty-second part in width of the whole body-length; in individuals 
living at a lower temperature the gill-sac of the same pair of legs gave the 
twenty-fifth in length and the fiftieth part in width of the body-length. 
It seems that temperature has upon the gill-sacs a more vigorous effect 
than the concentration of the salt water; on the other hand, the density 
of the salt water has a stronger influence on the posterior branchial 
lobes. ‘The circumstance is hereby illustrated, that in the first, red 
variety of A. salina (varietas a, description farther on), the gill-saes are 
smaller, but the posterior branchial lobes are larger than in A. salina. 
Not to mention so many figures, I point to the width of these append- 
ages, since in these forms they differ in length little from each other. 
In measuring the specimens of A. salina at a density of 13° Beaumé, 
and the specimens of the first, red variety at a density of 16° Beaumé, 
at one and the same (moderately low) temperature, I found that the 
width of the gill-sacs of the eighth pair of legs in A. salina was the 
thirteenth, but in the stated variety it was the forty-ninth part of the 
body length, and that in A. salina the width of the posterior branchial 
lobes was the thirty-fifth, but in the red variety it amounted to the 
thirty-second part of the whole body-length. In this manner, besides 
the fact that the specimens of this variety were collected at a higher 
density of salt water than the specimens of A. salina, their gill-sacs are 
nevertheless smaller than in the latter; but the posterior branchial 
lobes are larger in the variety than in its species, this corresponding 
already with the larger quantity of salt contained in the water. Such. 
