PACKARD] TRANSFORMATION OF ARTEMIA. 479 



variety of Daphnia onagna, the latter variety being itself again an inter 

 mediate form between the typical Daphnia magna and D. pulex. If we 

 would restore the middle radical form, which gave origin to Daphnia 

 magna and D. pulex, we would receive a form most similar to our Daph- 

 nia magna varietas, in the production of a still farther allied, a prototype 

 for the largest number of Daphniss, we would arrive at a form most 

 similar to Daphnia degenerata from the salt-water ditches. Such ex- 

 amples show that, oiving to the neighborhood of salt ivaters in which the 

 generations of the fresh-water species distribute themselves and in 

 which they change under retardation of development, the species them- 

 selves in fresh waters of such districts deviate to a certain degree from the 

 typical form, i. e., they change toward the direction of the next lowest 

 species of their genus. In consequence of the existence of such an ele- 

 ment in these districts the area of distribution of the species changes; 

 but as the center of this area will be found somewhere between the 

 fresh-water and the salt-lake element, the aberration of the fresh-water 

 generations in the neighborhood of salt-lake waters, in which the gene- 

 rations of the fresh-waters pecies already considerably changed them- 

 selves and become retarded in their development, is ea!<ily understood. 



The salt ditches, which distribute themselves on saline soil near Odessa 

 between the sea and the two salt lakes, the Chadschibaisky and the Ku- 

 • jalnitzky, become fresh-water ditches after gradual elevation, and sim- 

 ultaneously begin to become populated with fresh-water generations, 

 whereby these generations form, to a certain degree, changeable transi- 

 tions toward the more changed salt-lake forms. Some of the ditches six 

 years ago containing salt water of about 3° to 4° Beaurae, and inhabited 

 by the salt-water species, Branchipus spinosus Milne Edw., now contain 

 nearly fresh water, and are populated this year (1876) with the fresh- 

 water forms Daphnia magna Leydig varietas and Cyclops brevicaudafus 

 Glaus, slightly changed in the direction toward the lower forms. In re- 

 lation to the latter, a transitory form of Cyclops brevicaudatus varietas 

 h^ and Cyclops brevicaudatus Claus, was to me of great interest. In the 

 real fresh-water Cyclops brevicaudatus the extreme inner one of the four 

 furcal bristles is twice as long as the extreme outer, or actually the twenty- 

 fifth part shorter than the double length of the last outer bristle ; in gener- 

 ations inhabiting less saline ditches the extreme inner bristle is, on an 

 average, the sixth part shorter than the double length of the extreme 

 outer. In Cyclops brevicaudatus varietas b. the extreme inner furcal 

 bristle is but little (one-quarter) longer than the extreme outer. The 

 adult forms of the changed generations of Cyclops brevicaudatus in the less 

 salty ditches exhibit nearly the same relation of body parts, as seen in the 

 young, immature, pure fresh- water forms of the same species ^ but the ma- 

 ture individuals of said variety correspond in this point loiih the younger 

 individuals of the species. 



To this I have to refer also the interesting influence of the surround- 

 ings ui3on the development of specimens of Artemia. The growth of 

 the specimens of Artemia salina in salt water of high density and at the 

 same temjierature proceeds at least twice as slow as the growth of speci- 

 mens of Branchipus ferox in less saline water. Abstractedly from the 

 fact that the growth of specimens of Artemia salina requires much 

 time, sexual maturity appears much earlier in proportion to the full de- 

 velopment of body-parts, than in Branchipus. At a high concentration 



1 Consult my iiajjei" in the "Sclirilten" of the Neoriiss. Soc. of Naturalists, vol. iii. 

 part 2, pp. 32 to 36, aud 74 to 77. Also on the domestication of Cyclopidai, ibidem, 

 pp. 84 to 93. 



