266 78 



The almost incredible formshifting power of the animal depends chiefly upon the 

 muscle system. The excretory system exhibits a series of peculiar anatomical struc- 

 tures. The canals are not to such a high degree curled up, as is the case especially 

 with A. priodonta. On each side of the bodj' run three canals, the two of the struc- 

 ture indicated by Hudson-Gosse as tubes of loose granular stuff; the third one 

 is somewhat clearer, perhaps with more solid walls, bearing about forty and often 

 fifty vibratile tags; this canal has a peculiar cul de sac appendix, running down 

 in the vicinity of the dorsal antennæ. How these three canals are connected with 

 each other I do not know with certainty; in their whole course they are almost 

 free of each other, only meeting near the corona and the bladder. This, when fully 

 distended, may be extremely large, filling up a great part of the body cavity. The testis 

 is rather small; the structure of the ductus seminalis and urogenital canal with the 

 opening of the vesicle just at the boundary between both is in accordance with the 

 facts found in the other three species. Dorsally round the testis there is deposited 

 stored nutriment in the shape of yolkmass in different amounts. — Size of a male 

 500 p, of female 1500—2000 ^(. 



This very peculiar Rotifer I have only met with in a single pond, extremely 

 shallow, rich in organic matter; as it was found, the pond two months before 

 had just been dried out; before, it was almost overgrown with vegetation, and the 

 water a frumenty, overfilled with green algæ. 



It was in the last part of August that the first sample was taken, and till the 

 middle of October the pond was visited every week. The first time I found this 

 Rotifer, I immediately saw that I had found a population of an Asplanchna which 

 corresponded with those colonies which were found bj' Powers. In the following I 

 shall try to give an extract of his paper. 



A. amphora was living in vile pools on the alkaline flat west of the city of Lincoln, 

 Nebrasca. The water was here dark brown with alkali and the essence of compost. 

 It was shown that the culture only thrived well where the "water" had the original 

 composition of the native home of the animals. In nature, every rain-shower which 

 diluted to an appreciable extent the vile ponds in which this Asplanchna flourished, 

 resulted in the death of the entire stock, which was only replaced by the hatching of 

 new individuals from resting eggs. The main result of the studies of Powers was, that 

 A. amphora was a trimorphic species divided into three different forms: the saccate, 

 the humped and the campanulate form. The first (A) was invariably produced from 

 resting eggs, multiplying by rapid parthenogenesis through several generations. It 

 always preponderated in the beginning of the year, but was then rarer and rarer. 

 It was succeeded by the humped form (B), originating from the former by rapid 

 saltation; it produced chiefly its own type; the size of the humps may differ very 

 much according to nourishment. Owing to canibalism then a third form (C) arose, 

 the campanulate type, which reproduced both its own form and B. The three forms 

 differ from each other in the following main points: in A the corona is about equal 

 to the diameter of the body; and nearly circular in outline; there are no humps; 



