PACKARD. ] TRANSFORMATION OF ARTEMIA. A471 
summer of 1870, then not yet being aware that, according to Professor 
Siebold’s investigations, no males could be developed! The same error 
crept into an extract of the protocol, sessions of the zoclogical part of the 
third meeting of Russian naturalists at Kiew contained in this journal 
(Zeitsch. f. w. Zoologie), and this gave Professor von Siebold occasion for 
a timely remark.? Taking advantage of the present occasion to correct 
the mistake, observing that it was not printed in my paper, although 
the latter, together with the report, was prepared in the same session, 
I have yet to add that Artemia salina becomes accustomed to gradual 
changes in the concentration of salt water in the lake, as well as in do- 
mesticating them, and then becomes fitted to stand a very high or very 
low density of the water, so that either of them form a suitable envi- 
rofment. In rapidly changing the concentration of the salt water the 
same is rendered unfit to sustuin life, changing the manner of obtaining 
food, and produces, at the same time, in a state of nature, the appear- 
ance of males in forms to which parthenogenesis is peculiar. 
I had atready observed this in Artemia in the lake, but saw this es- 
pecially in Daphnia with artificial domestication of non-isolated females, 
that the males of the domesticated species first appear on the most ex- 
treme life-sustainable limits of the surrounding elements, 7. e., as well 
at a too low as at a too high temperature. 
If we domesticate the fresh-water species, Daphnia magna Leydig, in 
weak salt water, which they stand well, there appear, at this compara- 
tively rapid heightening of density of the salt water, males and fertil- 
ized eggs at such a moderate temperature, at which ordinarily the same 
species in fresh water propagates parthenogenctically. 
In the Hadschibei Lake occurs Daphnia rectirostris Leydig, at a den- 
sity of the salt water of 5° to 8° B., especially in spring and fall; the 
same disappearing in summer at a higher density of the salt lake, 
while before the females often in the middie of the summer cease to pro- 
pagate parthenogenetically, bearing as in fall fecundated eggs in 
ephippia. 
Altogether I produced during the artificial domestication of Daphnia 
the appearance of males and fecundated eggs through rapid augmenta- 
tion of the density of the salt water as well as through rapid increase of 
temperature. However it is difficult to say which will be the mean of 
concentration for a known species of Artemia, because a slightly less- 
ened density, though favorable for the growth of the individual, weakens 
its power of propagation, while a heightened density augments (or sup- 
ports) propagation, on the other hand this being a hindrance for the 
development of the individuals. The undiscovered mean of density, it 
seems to me, must be between these two points, the most extreme limits 
of the favorable condition of the surrounding elements being then out- 
side of those two points. 
On these limits we must find a density at which the males appear in 
the lake in great multitudes, as severel observations and analogous in- 
vestigations on Daphnia have demonstrated. 
I therefore recede from iny opinion that the males of Artemia appear 
at a mean density of the salt water, if the mean density is determined 
between that of favoring the development and that of assisting the pro- 
pagation. 
Until now I have found the greatest number of males of Artemia sa- 
lina in the Hadschibei Lake in the middle of the summer of 1870, at a 
