PACKARD.] TEANSFOEMATION OF ARTEMIA. 477 



counting in all apodous segments, while in the Hungarian forms the 

 length of the egg-sac equals the whole postabtlomen, excluding the ab- 

 dominal appendages. Besides, in Branchipus ferox of the salt-water 

 ditches the egg-sac is not spindle-shaped, only elongate, often entirely 

 oval, i. e., not only shorter, but also broader, as in the form diagnosed 

 by Chyzer. In our salt water ditch forms the furcal lobes average in 

 length the eighth part of the body length, inclusive of the furcal lobes; 

 in Chyzer's Hungarian form, as shown by tlie measurements, the furcal 

 lobes average the fourth and a half part of the whole body length in- 

 cluding them, that is, they are much longer in the Hungrjrian form. 

 The most important difference consists in that wbilein Bratiohipus ferox 

 of our salt ditches the furcal lobes have both edges bristled, in the form 

 described by Chyzer only the inner edges of the lobes are bristled. 

 Lastly, our salt-water ditch form measures, inclusive of the abdominal 

 lobes, seventeen to twenty-two mdlimeters, the Hungarian form twenty- 

 nine to thirty -four millimeters. Our salt-water form approaches in all 

 other respects the diagnosis of Chyzer, and does not disagree with the 

 determinations of Milne-Edwards and Grube. 



Besides the difference between the specimens of our salt-lake-water 

 and the Hungarian fresh-water forms of Branchipus ferox, -we Und, after 

 strict examination of the matter, that the bristles of the furcal lobes in 

 our salt-water- ditch forms, only in young animals shortly before becom- 

 ing sexually mature, commence at the base of the lobes in one height, 

 and that on getting older the number of bristles is lessened along the 

 exterior edge, and that in the adult, and especially in old individuals, 

 the bristles on the exterior edge of the furcal lobes will be seen to com- 

 mence more than twice lower than on the inner edge of the same. At 

 a length of the furcal lobes of 2.5'"^", in the adult form, the bristles be- 

 gin on the inner edge at a distance of 0.24'"™ from the base of each lobe, 

 but on the exterior edge they begin at a distance of 0.52°^™ from the base 

 of each lobe. The bristles on the exterior edge of the lobes are in adults 

 of this form more than twice shorter than those on the opposite inner 

 edge, especially on the first half of the furcal lobes. The younger the 

 individuals are the more trifling is the dijferenee bettceen the bristles of the 

 inner and outer edge of the lobes. Furthermore, in the salt-water ditches 

 of low density such generations of Branohipus ferox live, whose individ- 

 uals have an average size of about 22"'"'. In these larger specimens 

 the exterior edge of, this or that abdominal appendage in the adult 

 state has no bristles from base to the middle of the lobes. The bristles 

 of the exterior edge are also shorter and more sparsely distributed than 

 in the preceding form. Their egg-sac usually reaches down to the 

 middle of the fifth apodous segment, and is a little longer than the egg- 

 sac of the preceding form. The ditches with nearly fresh, scarcely 

 saline-tasting, water harbor also still larger specimens of Branchipus 

 ferox, measuring some 25"'™ in average length. In these large individ- 

 uals in mature age the exterior edge of either furcal lobe is without 

 bristles from base down to over the middle of each lobe. The remain- 

 ing bristles are again still more sparsely i)laced, and also shorter than 

 in the preceding form; the egg-sac is also a little longer. 



Specimens of Branchipus ferox, collected by me in ditches on Taman 

 Island, in the neighborhood of the city of Kertsch, represent another 

 link in the series of transitory forms between the extreme generations 

 of the salt-lake and Hungarian fresh-water specimens. In the Taman 

 specimens, which have a length of 30™'", the egg-sac reaches to the 

 middle or to the end of the fifth apodous segment of the abdomen, the 

 furcal lobes having nearly the same length as those of the Hungarian 



