PACKAKD.J TEANSFOEMATION OF AETEMIA.. 503 



the former already at 20° Beaum6 represent a just as far degraded o-r 

 retrograded form as do the hitter at 23° or 24P Beaum(5, and that the 

 former occur principally in one, but the latter in another, now cut-off 

 part of the Kujaluitzki salt lake. For better distinction I shall call the 

 former the smaller, the latter the larger form with the characters of A. 

 milhausenii. 



Did this Artemia, with the characters of A. miniausenii, one form of 

 A. saliiia, change by the influence of the surroundings, or one by the 

 influence of the same in the development-retarded form*? To this ques- 

 tion the characters themselves, and the course of posteinbryoual devel- 

 opment of this modified and also in development retarded form, answer. 

 I^ot only characters show themselves in this form i3eculiar to the younger 

 age of A. salina, and originated from retarded development, but also 

 newly acquired to the surrounding adapted characters. The young 

 individuals of A. salina and its variety have, as is known, in the begin- 

 ning no furca, but it develops much later. This circumstance testifies 

 that in adults with the characters of A. milhausenii no furca has been 

 formed, owing to retarded grovv'th. But we must consider that in those 

 transitory formsbetween J-.sa^i«aand J..7??i/A.,which in mature and old 

 age have a little-developed furca, with a very small number of bristles, 

 have, in still young age, just before the appearance of sexual maturity, 

 and shortly after the same, a still more developed furca, with a larger 

 number of bristles preserved, than in old age, during which this part at 

 one and the same salt capacity of the icater more degrades. This phenom- 

 enon can still be better noticed in the domestication of successive gen- 

 erations of A. salina in salt water of gradually increased concentration, 

 wherein that period, during which the furca mostly develops, shortens 

 with each following generation, the development of the furca becoming 

 a weaker one, appearing in shorter time-spaces. It is important that this 

 period includes the space of time immediately before and partly also 

 after the appearance of sexual maturity, in the beginning of mature 

 age; also in those specimens in nature in which in later, mature, and 

 old age altogether no furca exists, a little developed appears in said 

 period, partly with bristles, or only in later generations, by the influ- 

 ence of the surroundings in the same direction, this phenomenon of char- 

 acters of higher original form is more and more obliterated. All these 

 phenomena prove that the absence of the furca in the forms with the 

 characters of A. milhausenii depends upon retarded development of the 

 organization of the generations, not only from the appearance of sexual 

 maturity still before the full development of the body parts, but also 

 from the immediate influence of the salt water of higher concentration, 

 at which the appendages just beginning to develop became as if atro- 

 phied. There are many similar examples of retrograde development of 

 the form and of the individual. 



The greater length and slenderness of the postabdomen in the speci- 

 mens with the characters of A. milhausenii compared with the part in 

 mature and still more in younger A. salina^ proves with certainty that 

 the organization of such specimens in this relation depends almost entirely 

 upon the immediate influence of the element, but not upon an indirect 

 influence, i. e., from the mechanical jjressure of the salt water, and the 

 later appearance of sexual maturity, and not from the retained growth 

 and the appearance of sexual maturity before the complete development of 

 the body-parts. Had the ijostabdomen of the specimens with the char- 

 acters of A. milhausenii formed as a consequence of retarded growth and 

 in comparison to A. salina earlier and before the full development of 

 the body-parts ensuing apiDcarance of sexual maturity, this postabdo- 



