ATA GEOLOGICAL SURVEY OF THE TERRITORIES. 
For the purpose of illustrating this, 1 have chosen Daphnia rectirostris 
Leydig (Moina rectirostris Baird) and Branchipus ferow Chyzer. 
Daphnia rectirostris occurs here in large numbers in fresh-water basins, 
brine ditches, and also in the Chadschibaisky Salt Lake. In the latter 
they occurred at a concentration of from five to eight degrees of 
Beaumé’s areometer. Two characters are seen in the Daphnia rectiros- 
tris living in so diversified elements, the former depending on the latter. 
It appears firstly, that in salt water, and especially in the more saline 
Chadschibai Lake the middle temperature is lower, #. e.. the temperature 
more favorable for the life of Daphnia rectirostris than the temperature 
favoring the life of the same Daphnia in fresh water, so that the Daph- 
nia, being in reality a summer form of the fresh waters, changes in salt 
water into a fall form, occurring till the beginning of winter in the salt 
lake at a concentration of 7° to S° Beaumé in immense quantities, even 
remaining viviparous at 2 temperature at which the individuals of the 
fresh-water generations of the same species could live no longer. Sec- 
ondly, the individuals of the salt-lake generations of Daphnia rectirostris 
represent a degraded or retrograde form of the fresh-water generations 
of the same species, differing from the latter the more the higher the 
concentration of the salt-water basins in which they occur increases, 
so that the individuals of the salt lake differ more from the fresh-water 
forms than the individuals living in salt ditches. 
So much do the forms of Daphnia rectirostris from the salt lake differ 
from these of the fresh waters that they could be regarded as a separate 
variety of Daphnia rectirostris, although it is but a transformed gener- 
ation retarded in its development, and changed under the influence of 
the su rroundings of Daphnia rectirostris inhabiting the fresh waters. 
On account of various observations and experiments, I presume that 
the peculiarities of the salt-lake form of Daphnia rectirostris are entirely 
dependent on the properties of the salt water which they inhabit. 
Daphnia rectirostris cannot stand in summer a density of the water 
of the salt lake of 6° B., while it lives in great quantities in the same 
salt lake at a density of 8° B. in the fall, toward the end of October 
and in November, being than viviparous, that is, at such a season in 
which the fresh-water form of our Daphnia has already ceased to live. 
This is not an extraordinary phenomenon, considering that a certain 
aeration of the water is unconditionally necessary to sustain the life of 
Daphnia rectirostris, and that it is unimportant by which means the 
aeration of the water is regulated. Agreeing with the physical law 
the less the aeration of the salt water, the higher its density becomes, 
which results that fresh water must contain more air than any salt 
water of the same temperature. It consequently follows that also in 
a salt water of certain concentration at a corresponding lower tem- 
perature the same quantity of air as in fresh water could be contained. 
It is obvious that the quantity of air in the water of the Chadschibai 
Lake toward the end of October and at a density of 8° B. could approxi- 
mately be the same as that in fresh water during the summer, and 
therefore the processes of nutrition in the organism of Daphnia rectiros- 
tris could in reality be as favorable in both the fresh and salt water. 
Though analogous in general, they differ singly from each other, as, for 
instance, by the higher pressure of the more dense water, which density 
again depends on the quantity of salt and the lower temperature of the 
water. Dependant on such differences between salt and fresh water 
are also partly some differences in the organization of the salt and fresh 
water forms of Daphnia rectirostris. 
In the females of the Chadschibai Lake, the penicilli or fascicles of 
