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I saw it more than 25 years ago; it was found in the above-named little duck pond 

 lying very near the birth place of my good friend, the celebrated Danish Naturalist 

 Dr. Th. Mortensen. The drawing derives from these specimens. Later on I never 

 found the animals in this little pond, and when I explored the pond again in 1921, 

 I found it quite altered and with hardly any Rotifers in it at all. I have been in 

 search of the animal during all these years; not till 10/VIII 1921 did I find it again 

 in another duck pond in the little village of Fjenneslev near Sorø. 1 had the good 

 fortune to come across it in the sexual period and got several males. In the samples 

 were only humped females and males, but it was in the last part of the sexual 

 period, the pond being almost dried up. In 1922 I never succeeded in finding the 

 species again. 



I am not quite sure that my determination is quite right. The species being 

 equipped with large humps, well developed in all the many females and in the males 

 which I have seen, but really often withdrawn when swimming, it is impossible to 

 refer it to A. Brightiuelli. Equipped with one single eye, conspicuous humps and horse- 

 shoe-shaped ovarium the animal must be referred to the group A. intermedia, am- 

 phora and Sieboldi. As the jaws have a large innertooth and as there are more than thirty 

 vibratile tags, it cannot be referred to intermedia, a species which in mj' opinion is 

 rather doubtful. A. amphora is reallj' a proteus among the Asplanchna species; only 

 if a population from a pond were observed the whole year round, would it be possible 

 with certainty to determine A. amphora from the other species; as however I never 

 found the campanulate and saccate forms, characteristic of A. amplwra in the colonies 

 from Frerslev and Fjenneslev, and the first-named colony was observed four times 

 in the course of two months (May — June), I do not think it can be correct to refer 

 these populations to A. amphora. Comparing my material with the long descriptions 

 of HuDSON-GossE and Leydig I find great conformity upon all essential points; I 

 only lack the two humps upon the neck below the wheel-organ but as even these 

 humps are subject to great variation I cannot see that it would be impossible, only 

 because of that, to refer my specimen to this form. 



It was in this species that Daday (1889, p. 140) observed the polymorphism of the 

 Asplanchnadœ. He found two different forms of females, partly saccate, partly humped; 

 both forms are able to produce partly females of their own form, partly those of others, 

 parth' males and, after fertilization, resting eggs. I then found a peculiar species in North 

 Seeland; it was in May, and in the pond only the humped form existed which, during 

 swimming, had \er\ often drawn in the humps. I therefore supposed, (1898, p. 200) that 

 there reallj' only existed one form with great power of altering the shape of the bod}'. 

 At that time I did not know Wierzejski's paper (1893 a, p. 57); he too had observed 

 the phenomenon and interpreted it in accordance with v. Daday. In 1911 Lange (p. 433) 

 found an Asplanchna at Schönau near Leipzig. By studies in cultures, he showed that 

 the females deriving from resting eggs were always of the saccate form, and that the 

 humped form did not arrive before the third generation. The appearance was quite 

 sudden. From his own observations on A. amphora Powers (1912, p. 536) concluded 



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