256 68 



should only have four Asplanchna-sjiecies with a horse shoe-shaped ovarium A. Bright- 

 ivellL A. Sieboldi, A. amphora and A. Silvestri. With regard to A. Brightwelli it may 

 he emphasised, that, even if tliere exist races of A. ß/'f^'/i^i/'e/Z/ with inner tooth upon 

 the rami (Powers), this is commonly not the case. Undoubtedly in numerous localities 

 there exists an Asp/anc/jna-species with a horseshoe-shaped ovarium; it does not 

 undergo any variation in form and the rami are always destitute of an inner tooth. 

 At all events this is the case in Denmark. These species are referred to A. BrighiweUi. 

 With regard to A. Sieboldi the polymorphism has been studied bj' v. D.\day 

 (1SS8, p. 140) WiERZEYSKY (1893, p. 57) and Lange (1911, p. 433), that of A. Sylvestri 

 by RoussELET (1913, p. 57) that of A. priodonta especialh' by Langhans (1906, p. 439) 

 and W.-L. (1908, p. 82) and that of A. amphora by Powers. I for one confess 

 that from the descriptions I am unable to distinguish A. amphora from A. Sieboldi 

 but suppose that provisionally it is most correct to keep them distinct. 



Asplanchna priodonta Gosse. 



Male : Gosse 1850, p. IS. 



Hudson-Gosse 1889, p. 123. 

 Daday 1891, p. 79. 

 Weber 1898, p. 378. 

 Tab. V, fig. 6; Tab. VII, flg. 1; Tab. VI, fig. 6—7. 

 HuDSON-GossE (1889, p. 123, PI. XII, fig. 2) describes the male as follows: 



The male differs hardly at all in its internal structure from that of .4. Ebbesbornii: though 

 verj- different in shape. Its sperm-sack is supported by a strip of tissue that hangs from the 

 head and resembles in shape and position the alimentary canal of the female. It is, however, 

 imperforate and structureless and seems to have no other office than to support the sperm- 

 sack and penis. The nervous ganglion unusually conspicuous. Two of its four diverging threads 

 pass downwards to the dorso lateral rocket-headed antennae, and two pass upwards to similar 

 antennæ on the two apices of the corona. By slightly compressing a male, I put beyond 

 question the fact that the contractile vesicle empties itself outward trough the cloaca; for 

 under shght pressure the vesicle contracted slowly, by stages as it were, collapsing partially 

 in separate ellorts instead of closing at once. As it did so, I distinctly saw, at each effort, the 

 gradual passage of a plug of fluid down the cloaca, dilating its walls as it went. Size male: 

 200—400 fi, female 600—1000 fi. 



The male of A. priodonta is most probably one of the most frequently' observed and 

 figured Rotifer males. Nevertheless, as far as I know, no better or more exhaustive description 

 than that of Gosse exists nor a better figure than that in Hudson-Gosse (compare f. i. this 

 figure with Dadays (1891: Tab. II, fig. 6 — 7, description p. 79) and the figure and description 

 by Weber (1898, p. 378). 



It must only be added that Masics (1890, p. 651) without describing the male has given 

 a good description and drawing of the male organs of A. priodonta. He gives the following 

 very interesting observation hitherto unique and not corroborated by any other observer: 

 "Tel est l'aspect ordinaire du canal deferent dont Ténorme diamètre semble peu en rapport 

 avec ses fonctions. La raison du diamètre considérable de ce conduit s'exqlique par ce fait que 

 (dans certains cas du moins) les spermatozoïdes sont rejetés à Textérieur dans un volumineux 

 spermatophore." Masius has observed the spermatophore three times and describes it as 

 follows: "II est sphérique ou légèrement allongé, jaune brunâtre et formé par la réunion 

 d'un grand nombre d'éléments chitineux, polyédriques, de dimensions variables. Les plus grands 



