PACKARD.] TRANSFORMATION OF ARTEMIA. 483 
at a very great density of the salt water, approaching the natural 
deposition of salt, or having attained the latter already, we find a great 
difference in the size of the gill-sacs and the posterior branchial lobes, 
since the appendages mentioned are considerably larger in the latter 
than in Artemia salina. To see this, we compare specimens of Artemia 
salina from the Chadschibai Lake at 9° Beaumé in the first half of Sep- 
tember with the degraded genera of this species! taken from the Kujal- 
netzki salt lake at 24° Beaumé, also in the first half of September of 
the same year, that is, at very different density of the salt water and at 
nearly the same temperature. Hereby we receive in middle average, 
and omitting fractions, the following figures: 
In Artemia salina in Septem- In degraded specimens of Ar- 
ber at 9° Beaumé— temia salina with the char- 
. acter of Art. milhausenii at 
24° Beaumé— 
the gill-saes yielded 
in length the 23, in length the 18, 
in width the 44 in width the 28 
part of their body-length; 
the posterior branchial lobes yielded 
in length the 17, in length the 15, 
in width the 36, in width the 24 
part of their body-length. 
The length of the body of Artemia salina was here taken together 
with the furcal lobes, exclusive of their terminal bristles, in the same 
manner as in the above stated experiment; the body-length of the 
specimens with the characters of A. milhausenti to the end of the abdo- 
men, as they have no abdominal furca. Since the furcal lobes form a 
part of the body of Artemia salina and partake of the nutrition like the 
other body-parts, I have not excluded them in my calculations, although, 
too, the relations without this furca, which is of inconsiderable length, in 
comparing the specimens of this or that species, scarcely vary. I also 
add that I took here, as well as in the above stated experiment, the gill- 
sacs and posterior branchial lobes of the eighth pair of legs, thouzh they 
are not the largest in this leg. These appendages in mature specimens 
increase in size from the first to the sixth pair of legs, on the following 
legs becoming somewhat smaller, without, however, there being much 
difference between the sixth and eighth pair of legs. The comparison 
in any case loses nothing, as the specimens have been compared after 
one and the same pair of legs. I took these appendages from the eighth 
pair of legs, coming nearer the mean figure, which would express their 
size in all pairs of legs. 
Not less different is also the form of the gill-sacs in the degraded 
generations with the character of Artemia milhausenit and in Artemia 
salina. For comparison it is better to take the gill-sacs from the mid- 
dle pair of legs, as they are of smaller size on the first two or three 
pairs of legs, and as if not fully developed, having a somewhat deviat- 
ing form in the last pair of legs, gradually broadening towards the end, 
becoming in Artemia salina, as well as in specimens with the characters 
of A. milhausenii, nearly uniformly rounded. In comparing the gill-sacs 
of the middle pairs of legs of Artemia salina and Art. milhausenii we 
see that these sacs in Artemia salina are of an elongated form and that 
1Compare my report in the Zeitschrift f. wiss. Zoologie, 1875, vol. xxv, 1st supple- 
mental part. 
