PACKARD. ] TRANSFORMATION OF ARTEMIA. 467 
brought along with the flood from the upper portion as well as from the 
surrounding brine ditches near the same. 
After restoration of the embankment the density of the water of the 
lower part rapidly increased, showing already in the summer of 1872 
14°, in 1873 18°, at the beginning of August 1874, 23.59, and after a 
continued drought in September of the same year 25° ‘of Beaumé’s 
areometer, at the latter time the lower part of the lake beginuing to 
deposit salt. 
Simultaneously Artemia salina gradually degraded from generation 
to generation, so that toward the end of the summer of 1874 the majority 
of individuals were without furcal lobes, showing then all the specific 
characters of Artemia muehthausenit (Fig. 6). In 1871 Artemia salina, 
or better, one of its varieties, had moderately large furcal lobes, and on 
each of them eight to ten, seldom 15, sete, distributed over both sides 
and the tips (Ifig. 1). 
In the successive generations in the beginning of the summer of 1872, 
these furcal lobes were already smaller, with but 3 to 5 or 3 to 4 sete, 
the salt water then showing 14° Beaumé (Plate XX XIX, Figs. 2 and 3). 
In the same season of 1873 and at 18° B. the furcal lobes were still 
smaller, representing short conical knobs with but one, two, seldom 
three, setee (ig. 4). Toward the end of the summer of 1874, many 
individuals still possessed conical knobs or protuberances instead of 
farcal lobes, without or with but one seta on tip, but the majority of 
them were entirely destitute of furcal lobes and sete, as is the case in 
Artemia muehlhausentt with which these degraded examples were 
identical in their smaller size as well as in other characters (Figs. 5 
anc 6). 
L also obtained the same results by domesticating Artemia salina in 
salt water of gradually increased density or concentration, the examples 
obtained being identical with those from the Kujalinker Lake at the 
end of the summer of 1874 (Ariemia muehlhausenit), yielding also the 
same transitory forms. 
By a reverse treatment, @. e., by gradually diluting the salt water, I 
succeeded with Artemia muchihausenti in producing already, after sev- 
eral weeks, a furca in the form of conical knobs, with one terminal 
bristle, by which treatment also the development of other parts of the 
body assumed a direction toward the higher specialized varieties of 
Artemia salina, this being at variance with the retrograde development 
taking place in condensing the salt water. 
It is remarkable that the gills of these animals enlarge in proportion 
or in ratio with the density of the water, so that in the form without 
fureal knobs (Artemia muehlhausenti) the surface of the gills is much 
larger in proportion to the size of the body than in Artemia salina. The 
gills of the former especially enlarge in width. I draw the inference 
that as the water of higher density contains less oxygen these Crusta- 
ceans adapt themselves by gradually enlarging the surface of the 
breathing apparatus. 
Concerning the gills, I have to state that they are elongate in Artemia 
salina and oval in A. muehlhausenti (Figs. 7 and 8). The width of the 
gills in A. salina average scarcely half of their length, in A. muwehl- 
hausenti two-thirds of their length. 
As regards the length of the body, I may mention the following 
measurements, showing the proportionate sizes of the gills; In Artemia 
salina the average length of the gills at a density of 10° B. is the one- 
twenty-first part of the body length, the width being the one-thirty-ninth 
part of the same. In Artemia muchlhausenii the average length of the 
