77 265 



also seen the humped males in utero. He has further observe<l that A. amphora may entirely 

 disappear from the pond, whereupon A. Briglilwellii turned up in great abundance. 

 Daday (1891, p. 85) only says: "Körper conisch mit zwei Seitenfortsätzen." 



Description. Body form very peculiar; almost triangular willi circular lo]), 

 a triangular base, a broad dorsal side and rather narrow rounded ventral side; on 

 each of the two side-planes are Iwo sleeve-like prolongations, two humps of Ihe 

 cuticle; they differ in size and form from specimen to specimen, are not equally 

 developed at all times of the year, and have never quite the same appearance in 

 different ponds; they are often drawn in during the swimming motion and can 

 suddenly be unfolded; this always takes place, when the wheel-organ is withdrawn 

 or when the swimming direction is altered. They are always destitute of inner or- 

 gans. The whole animal is extremely hyaline, crystalline. I have never found more 

 than two humps. The coronal disc is conical with two apices. The ciliary wreath 

 is a simple ring of cilia, as far as I have been able to see, without any interrup- 

 tion dorsally or ventrally. The brain is large, flattened, much broader than long, 

 indistinctly divided into two parts, and sending nerves off from the corners to the 

 coronal disc and to the body behind. On the coronal disc are found four hairtufts, 

 each of these receive nerves, as shown in the figure of the animal, seen dorsally. 

 There is only one red eye; no eye-spots in the corona; four long nerves, two ven- 

 trally and two dorsally run down to the lateral antennæ. Seen from the dorsal or 

 ventral side, a long cylindric rather narrow faintly curved body is seen, hanging 

 down from the corona; during swimming the organ is seen dangling hither and 

 thither; it differs in size and development from specimen to specimen; it has 

 hitherto only be observed in A. intermedia by Hudson. Like this author 1 regard 

 it as a rudiment of the alimentary canal; at all events it does not reach the testis 

 w^hich, just as in A. Brightwelli, is free and has no intestinal band connecting it 

 with the wheel-organ. The muscle system is, especially in this form, very conspi- 

 cuous, on the other hand owing to the peculiar form of the animal difficult to 

 study. Seen dorsally A. amphora exhibits some remarkable differences in the course 

 of the great retractors of the wheel-organ. As in the other species they really run 

 from wheel-organ to testis, but, if I am not mistaken, before they reach the wheel- 

 organ, they cross each other in a rather peculiar manner (see Tab. Vll, lig. 4), 

 perhaps this is a peculiarity in some individuals or in the whole population invest- 

 igated. Seen laterally it may be show^n that the other muscles dorsally and ven- 

 trally as well as those to the testis, are in full accordance with those of A. prio- 

 donta and A. Brightwelli; the special muscle from corona to testis in A. Sieboldi I 

 have not found here. Of peculiar interest are the four very conspicuous transversal 

 muscles, one of which crosses the bodj' on a level with the humps, dissolving 

 themselves into three or four very fine threads, fastened to the cuticula of the humps. 

 After these four more conspicuous bands, one or two other very fine threads, pa- 

 rallel with the others, are visible. The whole body, especially in the hind part, has 

 a very conspicuous wide-meshed network of fine threads, running below the cuticula. 



