PACKARD.] TEANSFOEMATION 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 kiter 

 age of the latter. Since the "vrhole development of these or those speci- 

 mens 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 wo 

 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. Tliis force was the sur- 

 rounding element of a certain composition, that is, the large salt capa- 

 city of the water alone, or iu 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 w^orthy of remark that the fact that 

 the adaptation to the element is accompanied by a retarded development 

 of the generations, as iu other cases the adaptation to the element in 

 these animals is accompanied by a lirogressive development of the gen- 

 erations; 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 iu 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 actiml 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 ])roper, 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 iu a given locality, and moreover iu 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, ueverthe- 



^The lowest ortranisms appear, by certain changes of the surronndmgs, in an incon- 

 siderable space of time to represent definire series of forms, which ^Ye are accustomed 

 to hold as sxK'cies. The begiuuing of my papers iu this direction relative to the low- 

 est organisms, foi-ms my article in the "Schriften" of the Neorussiau Society of Nat- 

 uralists, lci76, vol. iv. 



