482 GEOLOGICAL SURVEY OF THE TERRITORIES. 



sacs and the posterior branchial lobes of the domesticated mature speci- 

 mens of both vessels, measuring also the length of the body, finding also 

 the ratio between the length and width of these appendages to the length 

 of the bod,y, inclusive of the furca. The resulting figures gradually in- 

 creased with the strength of concentration of the salt water in one or 

 the other vessel in two different directions, the animals showing in the 

 fourth week of domestication a very considerable difference, which 

 plainly illustrated the increase of the length, and more so of the width, of 

 said appendages at a heightened density of the salt water, and also the de- 

 crease of those parts at a reduction of density of the water. Toward the 

 end of the fourth week the salt water in both jars attained a difference of 

 10° Beaum6, the gradually-diluted salt water showing then 3° Beaume ; 

 the salt water of gradually-increased density indicated 13° Beaume. 

 To compare the size of the gill-sacs and posterior branchial lobes of Ar- 

 temia salina at decreasing and increasing density of the salt water, in 

 measuring I searched for figures which indicated which part of the body- 

 length the length and width of these or those appendages in these or 

 those specimens formed. During the fourth week of the above-men- 

 tioned period of domestication I obtained the following figures as aver- 

 age results in two diverging directions : 



At a decreased density At an increased density 



of the salt water 



the gill-sacs yielded 



in length the 24, 3, in length the 22, 4, 



in width the 46, 5 in width the 40, G 



part of the entire body-length ; 



the posterior branchial lobes yielded 



in length the 17, 6, in length the 16, 8, 



in width the 38, 9 in width the 34, 9 



part of the entire body-length. 



I have to remark that toward the end of the period of domestication 

 the resulting figures in the measurements showed considerable oscilla- 

 tions. The cause of it is that in salt water of extremely decreased or 

 extremely increased density the animals soon became so short-lived 

 that the older individuals, as well as the younger just before or soon 

 after becoming sexually mature, died. The relation of the body-parts 

 in such young, though sexually mature individuals, resembles in some 

 degree the relation of the body-parts in young immature individuals 

 in another surrounding element, then normal for the species; for we 

 observe»also a slight retardation of growth in a suddenly produced ex- 

 treme decrease of the density of the salt water the same as in the in- 

 crease of the density of the salt water. In insuificiently gradually 

 diluting the salt water the individuals of Artemia salina die, as it were, 

 of debility, which cause lies probably in the heightened oxidation in the 

 organism dependent on the increased quantity of air in diluted salt 

 water. The highest development of the furca and the greatest number 

 of its bristles are not incongruous with the lowest density of the salt 

 water which this species can endure for a longer or shorter time, but it 

 is congruous with a concentration not much lower than that peculiar to 

 the species. The more gradual the concentration of the salt water in 

 the domestication of successive generations of Artemia salina is changed 

 the more deviates the mean (tor this species) favorable concentration 

 from that concentration which is the mean for it in free nature. 



In comparing Artemia salina with those degraded forms and genera 

 of this species exhibiting the characters of Artemia milhausenii, living 



