486 GEOLOGICAL SURVEY OF THE TERRITORIES. 



other species of crustaceans examined by me, we can observe all these 

 nidditications of the influence of the surroundiugs upon the otganism. 



The formation and full develo])meut 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 temperattire ; since hy a low- 

 ering of iemperatiire the size of the gill-sacs decreases, by a heightening 

 of the temperature they enlarge. 1 do not possess suliicient measure- 

 ments concerning the posterior branchial lohes 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 hy lowering the 

 temperature. Putting temporaiily the posterior branchial lobes aside, 

 I shall treat of tlie gill sacs only. 



In measuring the gill-sacs in specimens of Artemia salina^ gathered 

 in the first half of September out of the Chadscliibai Lake, I was sur- 

 prised at the figures obtained by the relatfou of their size to the length 

 of the body, deviating tar 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 13° Beaume, 

 had even a little smaller gill sacs than the specimens collected in sum- 

 mer at 9° Beaume, from the Chadschibai Lake. Subsequently, 1 di- 

 vided the young and old specimens taken from the Kujalniker Lake 

 at a density of 13° Beaumue into two sections and domesticated one 

 section at an average temperature of 14° [Eeaumur?] the other section 

 at an average of temperature of 7°+ Eeaumur. 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-sacs, especially in width, considerably smaller. In indi- 

 viduals living in higher temi>erature, 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 i^air 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 v;ater ; on the other hand, the density 

 of the salt water has a stronger intiuence on the posterior branchial 

 lobes. The circumstance is herebj' illustrated, that in the first, red 

 variety of A. salina (varietas «, description farther on), the gill-sacs 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 ai)pend- 

 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° Beaume, 

 and the specimens of the first, red variety at a density of 10° Beaume, 

 at one and the same (moderately low) temperature, I found thr.t 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 J., salina, their gill-sacs are 

 nevertbeless smaller than in the latter; but the i)osterior 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 



