PACKARD.] TRANSFORMATION OF ARTEMIA. 48l 



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 

 Arteraia, 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 is, 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-sacs 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 Ililhausenii, living at the highest density for Artemia, and that, as 

 we will see, the males of that race of Artemia saliyia (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. 



II. — On the Gill-sacs and the Posterior Branchial Lobes in 

 Artemia and Branchipus. 



1 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 0. Claus (in his paper on Branchipus stagnaMs 

 and Apus cancriformis) "Kiemensackchen"^ (gill-sacklet). 



Grube calls it "unterer Branchialanhang'" (lower branchial append- 

 age). 



S. Fischer called it "unterer Branchialsack'" (lower branchial sac). 



The posterior branchial lobes are called by Glaus {ihidem) "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 ofincreased density. 



Specimens of Artemia salina taken from the Chadschibai Lake, show- 

 ing a density of 9° Eeaum^, 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 Avater 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- 



' "Abliancllungen der koniglicheii Gesellschait der Wissenschaften zn Gottingeu," 

 vol. xviii, 1873. 



2 " Bemeikungen liber die Phyllopodcn " in "Archiv fUr Naturgescliichte," 1853, p. 

 141. 



3.Mid<lendorf' s Sibirische Reise, St. Petersburg, 1851, vol. ii, part 1, p. 151. 



31 h 



