PACKARD.] TRANSFOEMATION 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° Beaume in the first half of Sep- 

 tember with the degraded genera of this species^ taken from the Kujal- 

 netzki salt lake at 24° Beaume, 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 iu middle average, 

 and omitting fractions, the following figures : 



In Artemia salina in Septem- In degraded specimens of Ar- 



ber at 9° Beaume — temia salina with the char- 



acter of Art. milhausenii at 

 24° Beaum^ — 

 the gill-sacs 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 3G, in width the 24 



part of their body-length. 



The length of the body of Artemia salina was here taken together 

 tcith the furcal lohes, 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. milhausenii 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, tlioui«h 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 i)airs of legs. 



Not less different is also the form of the gill-sacs in the degraded 

 generations with the character of Artemia milhansenii 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 fullj^ 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. 7nilhausenii we 

 see that these sacs in Artemia salina are of an elongated form and that 



1 Compare my report in the Zeitsctrift f. \riss. Zoologie, 1875, vol. xxv, 1st sup^jle- 

 mental part. 



