PACKARD. ] TRANSFORMATION OF ARTEMIA. 505 
proaches the end of the development, so that the young specimens of 
one and the same age, but, from a different element, do not correspond 
in this relation, and the younger age of the former concurs with the later 
age of the latter. Since the whole development of these or these speci- 
inens proceeds similarly, so must ‘the development itself depend upon 
the immediate influence of the surroundings, after which the organism 
of these or those forms develops, whereby that in the generations sums 
up what the external conditions in them produces; and what they as a 
consequence of the influence of the surroundings acquire. Here we 
must imagine the transfer of the course of development of a single in- 
dividual upon the course of development of particular animal forms. 
From all this it results that the gill-sacs of the young individuals of A. 
salina are in a certain age similar to the gill-sacs of the mature individ- 
uals of A. milhausenii, but the gill-sacs of the young individuals of this 
latter species are at the same period still larger, and obviously represent 
an addition in the organization of this form in comparison with A. salina, 
and a result of the influence of some force. This force was the sur- 
rounding element of a certain composition, that is, the large salt capa- 
city of the water alone, or in combination with heightened temperature. 
Hence, we see that the gill-sacs in A. milhausenii, together with some 
other parts of the body, testify to the retrograde development of this 
form under the influence of the surroundings as well as of the immedi- 
ate influence of this element. It is worthy of remark that the fact that 
the adaptation to the element is accompanied by a retarded development 
of the generations, as in other cases the adaptation to the element in 
these animals is accompanied by a progressive development of the gen- 
eratious; in another element by the, as regards this species, typical de- 
velopment of the body parts and sexual maturity. In the one and the 
other case the element effectuates a change of form in a direct and in- 
direct manner. Of course, nature effects this in a great measure, not so 
much by the change of the element as by distributing generations of a 
species in a highly varied element. 
Touching now the question, whether the specimens with the charac- 
ters of A. milhausenii, which in the course of several years and a com- 
paratively small number of generations issued from A. salina in the 
Kujalnitzki Lake, at a gradual heightening of the salt capacity, do repre- 
sent a species, or at least a variety, I must answer in the negative. If 
it turns out that the actual Artemia milhausenii of the authors, according 
to its structure and origin, is equal to the degraded specimens of A. 
salina, then it has no right to be regarded as a species proper, yea, not 
even to be a variety of A. salina, or of any other species, since the man- 
ner of its origin under the mentioned conditions contradicts the prevail- 
ing conception of species and race. Species and race possess a compar- 
atively great endurance of characters, and must originate in consequence 
of more or less widely spread distribution of generations of their pre- 
ceding or contemporary forms in a differentiated element (without natural 
selection or with it), but not owing to the modification of the surround- 
ing element in a given locality, and moreover in a brief space of time, 
in the course of perhaps four years.! 
Even if the change of the element at a certain rate of slowness can 
favor the change of form, the main cause of their origin must, neverthe- 
1The lowest organisms appear, by certain changes of the surroundings, in an incon- 
siderable space of time to represent definire series of forms, which we are accustomed 
to hold as species. The beginning of my papers in this direction relative to the low- 
est organisms, forms my article in the ‘‘Schriften” of the Neorussian Society of Nat- 
uralists, 1876, vol. iv. 
