488 GEOLOGICAL SURVEY OF THE TERRITORIES. 
of the water, at which it (the variety a.) forms the transition to the cor- 
responding variety of A. milhausenii, that is, at 15°, 16°, and 18° con- ~ 
centration after Beaumé’s instrument. In concluding, it results that at 
such a concentration of the salt water, at which the above stated meas- 
urements of A. salina showed themselves, 7. ¢., at 9° Beaumé, and the 
temperature of the month of September, we must obtain the following 
figures for this race: 
The gill-saes The posterior branchial lobes 
must amount in their length _ 
the 25th, the 16, 5th, 
in their width 
the 52d the 34th 
part of the whole body-length. 
The variety Branchipus ferox, hereabouts living in salt water ditches, 
and to which is peculiar a lesser concentration of the salt water, how- 
ever at a higher temperature than that peculiar to the species Branchipus 
spinosus, yields the following figures, in relation to the gill-sacs and 
posterior branchial lobes: 
The gill-sacs The posterior branchial lobes 
amount in length to 
the 24th, the 20th, 
in width ) 
the 56th the 43d 
part of the whole body-length. 
The variety Branchipus ferox (from salt-water ditches) is, in its leg- 
appendages and according to the element which it inhabits, in propor- 
tion to Artemia salina as Branchipus spinosus is to varietas a.of A. salina. 
Especially those generations of A. salina which live in salt-water ditches 
of about 4° Beaumé, or the generations of the second variety of A. sa- 
lina (varietas b.) are in relation to gill-sacs and posterior branchial lobes 
and some other characters, also in the element in which they live nearer 
the salt-lake generations (from salt-water ditches) of Branchipus ferox 
(varietas). I must add here that the legs themselves are longer in 
Branchipus ferox var. and in A. salina than in Branchipus spinosus and 
in A. salina varietas a., and that only on this account the posterior 
branchial lobes of the forms of the one or the other category relative to 
length have no great differences. But the length of the legs corre- 
sponds with that temperature and with that concentration of the salt 
water which is peculiar to each of these furms.! 
Concerning Branchipus medius mihi, we can nevertheless recognize 
abstractedly from the point that it forms a too isolated species in its 
characters and in the relation-figures of its gill-sacs and posterior bran- 
chial lobes, the result of the effect of the element in which it is dis- 
tributed, as I have mentioned in the description of this species.’ 
The knowledge of the effect of the surrounding element upon the gill- 
sacs and the posterior branchial lobes in these animals is important 
because the differences of size between these appendages, according 
to authors (Milne-Edwards, S. Fischer, Grube), represent no important 
species-characters. 
It is here the place to add a few remarks which show how far the 
life of A. salina depends on the air-capacity (actually the oxygen of the 
1Consult any paper in the ‘‘Schriften der Neurussischen Gesellschaft der Natur- 
forscher,” 1875, vol. iii, 2d part, pp. 297 to £00. 
2Ibidem, pp. 305 to 313 
