476 GEOLOGICAL SURVEY OF THE TERRITORIES. 



during a rather brief duration the sensory threads on the tips of the 

 antenitre become nearly three times longer than before the beginning of 

 domestication. 



We now find in comparing the fresh-water generations with the salt- 

 water generations of DapJmia rectirostris that the latter generations not 

 only changed in consequence of the immediate effect of the surrounding 

 elements, but also in consequence of retarded development under their 

 influence; and, furthermore, that the sexual maturity shows itself earlier 

 in the salt-water generations than the comj^lete typical development of 

 the body parts. The termination of the sensory antennas, the color of 

 the body, the lesser pinnulation of the bristles in the salt-water genera- 

 tions are principally dependent upon the immediate effect of the sur- 

 rounding elements. The smaller number of the above-mentioned spines 

 on the postabdomen principally depends upon the retarded develop- 

 ment under the influence of changed surroundings. In the latter case 

 the indi^'iduals commence, without awaiting the development of their 

 body parts, to augment, and are in that state a complete animal form. 



Brancliipus ferox affords a still more characteristic example of the in- 

 fluence of the salt-lake element. Milne-Edwards,^ whose words Grube^ 

 repeated in his diagnosis of this species, gives a brief description of 

 BrancMpus ferox from the neighborhood of Odessa. Ohyzer^ completed 

 his description from Hungarian specimens. The diagnosis by Oliyzer 

 of this species differs so much from that of Milne-Edwards that both 

 authors could not possibly have had one and the same form of Branchi- 

 pus, as we shall see later on. It is difflcult to understand why Milne- 

 Edwards does not mention the two so important characters of this 

 species, which ought to rank with the principal characters which Chyzer 

 enumerates. This is the conspicuous length of the egg-sac, and espe- 

 cially the tact that the abdominal appendages or furcal lobes are bristled 

 only on their inner edge. To this latter peculiarity Chyzer especially 

 l)oints out the characteristics of Brancliipus ferox. It is evident that 

 Milne-Edwards had a very closely allied form to that of Chyzer's, since 

 in the neighborhood of Odessa, wherefrom Milne-Edw-ards's form came, 

 generations of this species occur in salt, brackish, and fresh water, which, 

 ovving to their dependence of the density of the water basms, consider- 

 ably differ in their characters. The generations inhabiting salt-water 

 ditches of about 5° Beaume differ as nuich from the individuals inhab- 

 iting fresh water, es])ecially the Hungarian forms described by Chyzer, 

 as any species will.difl'er from another one. Had I not found all pos- 

 sible transitory forms between fresh- water and salt-ditch forms, had I 

 not convinced myself of the variability b}^ domestication of this form, 

 I should have regarded the salt-lake specimens as a new form. For 

 some time I really took them for a variety of Brancliipus ferox Chyzer. 

 At present, and after so many convincing results, I can only condition- 

 ally regard this form as a variety. 



To demonstrate how much the salt-lake generations of Brancliipus 

 ferox (from the salt-water ditches) differ from the Hungarian fresh- 

 water specimens, compare the following characters: The egg-sac of the 

 salt-lake BrancMpus ferox reaches in its length oidy to the beginning, 

 or to the middle, of the fifth apodous segments, but as the following 

 sixth, seventh and eighth segments are longer than the anterior seg- 

 ments, the egg-sac reaches scarcely to the middle of the iDostabdomen, 



'H:stoire naturelle des Crnstacdes, III p. 369. 



^Bemerkiuigvn iiber die Pliyllopoden, Archiv f. Naturg p. 142, 1853. 

 ■' Fauna UiigurDS Crustaceeu. Verliaudl. der zoologiscli-botauiscliGU Gesellschaft 

 in Wien, 1858, p. 516. 



