PACKARD.] TRANSFORMATION OF ARTEMIA. 481 
statements of the authors (Leydig, Claus, Spangenberg) has eight apo- 
dous segments of the abdomen, represents in its principal characters an 
Artemia-like form; however, it remains to be determined whether this 
species is peculiar to Summer temperature, of which we have a few inti- 
mations. It seems that the dependence of the quantity of air in the 
salt water upon its density, beside the mechanical effect of such a water, 
forms one of the main factors of the sexual and specific characters of 
Artemia, whose forms are distributed according to the various densities 
of the salt water, as the species of a known genus are dispersed ac- 
cording to geographical latitudes, or also after their appearance at dif- 
ferent seasons (annual species). Moreover, a certain concentration of 
the salt water 1s, probably again in consequence of a certain quantity 
of air, in accordance with the physiological processes in Artemia. I 
here omit the respiration and the changing of the gill-saes of Artemia 
with the changing of the concentration of the salt water, simply men- 
tioning the circumstance, that we most rarely find males with those 
lowest degraded forms of our Artemia, bearing the characters of Arte- 
mia Milhausenit, living at the highest density for Artemia, and that, as 
we will see, the males of that race of Artemia salina (varietas b.) in 
salt ditches occur, which are most progressively developed and which 
live, in comparison with our other forms, at the lowest density of the 
salt water, as will be explained later on. 
IIl._—On THE GILL-SACS AND THE POSTERIOR BRANCHIAL LOBES IN 
ARTEMIA AND BRANCHIPUS. 
I shall speak in this section of the relation of these appendages in 
Artemia and Branchipus to their external life conditions. First we 
have to agree as to the determination of these parts. The gill-sac in 
these forms is called by C. Claus (in his paper on Branchipus stagnalis 
and Apus cancriformis) ‘‘ Kiemensaickchen”! (gill-sacklet). 
Grube calls it “unterer Branchialanhang”’ (lower branchial append- 
age). 
8. Fischer called it “‘unterer Branchialsack” (lower branchial sac). 
The posterior branchial lobes are called by Claus (ibidem) “‘hinteres 
Branchialblatt” (posterior branchial leaf); by Grube, ‘“‘oberer Branch- 
ialanhang” (upper branchial appendage); by S. Fischer, “oberer Branch- 
ialsack” (upper branchial sac). 
The first which demands our attention is that the gill-sacs and poste- 
rior branchial lobes in Artemia and the salt-lake Branchipus enlarge in 
length and more so in width during the domestication of specimens, or 
still more of generations of these forms in salt water of increased density. 
Specimens of Artemia salina taken from the Chadschibai Lake, show- 
ing a density of 9° Eeaumé, I divided into two equal vessels, gradually 
diluting the salt water in one of them, but increasing the density of the 
salt water in the other. I kept the water in both vessels at equal height. 
In both vessels were old and young growing specimens. Both jars 
stood near to each other and were, with the exception of differently- 
concentrated water, as regards temperature and all other influences, 
under the same circumstances. The experiment lasted for four weeks, 
‘during which time I daily measured the length and width of the gill- 
'“Abhandlungen der kéniglichen Gesellschait der Wissenschaften zu Géttingen,” 
vo]. xviii, 1873. 
san Bemerkungen iiber die Phyllopoden” in ‘‘Archiv fiir Naturgeschichte,” 1653, p. 
3 Middendorf’s Sibirische Reise, St. Petersburg, 1851, vol. ii, part 1, p. 151. 
ol H 
