126 Dr. O. Zacharias on the Reproduction and 



mata anglica possessed neither jaws, nor pharynx, nor 

 stomach, but lived solely for amatory purposes*. Brightwell 

 and D airy m pie are entitled to perfectly equal shares in the 

 merit of this most important discovery, but hitherto only the 

 latter has been mentioned by name in the text-books. 



Some years afterwards (1854) Prof. Franz Leydig found 

 himself in a position to demonstrate separate sexuality in a 

 second example, a Rotifer newly discovered by him {Notom- 

 mata Sieboldii). The female of this new species has a great 

 similarity to that of Notommata anglica, but the male is very 

 differently constructed. It is especially by the presence of 

 four lappet-like arms (one pair situated at the neck, the other 

 issuing from the middle of the body) that this male is distin- 

 guishable from that of the English Rotifer. In this case also 

 it was proved that the male of Notommata Sieboldii possessed 

 neither pharynx, jaws, nor stomach. 



By these fortunate and important discoveries the notion 

 was gradually established that separation of the sexes occurs 

 throughout the Rotatoria; and Leydig expressed his (cer- 

 tainly not merely individual) opinion upon this point in the 

 following terms. He says : — " In their structure the Rota- 

 toria manifest too great a harmony for us not to draw the 

 conclusion from the sexual difference of Notommata anglica 

 and Notommata Sieboldii that the other genera also have the 

 sexes separated upon two individuals " f. 



The acumen and circumspection of Leydig soon succeeded 

 in diagnosing other male forms from the descriptions and 

 figures given by other naturalists. Thus Leydig established 

 as clearly as possible that Ehrenberg's genus Enteroplea 

 hydatina was erroneously described as a distinct genus, its 

 representative really being only the male of Hydatina senta. 

 Leydig also thought, and correctly, that Notommata granu- 

 lans would prove to be the male of N. brachionus. This 

 supposition, as is well known, was verified by F. Weisse (St. 

 Petersburg) . 



By the Breslau naturalist Prof. Ferdinand Cohn, who has 

 occupied himself in the most thorough-going manner with the 

 organization of the Rotatoria, the reproduction of these 

 animals was in 1854 made the subject of a special publica- 

 tion \. This is especially valuable, because Cohn was so 

 fortunate as to be able to confirm Ley dig's inferences by 

 experiment, and thus the incontrovertible proof was furnished 



* Phil. Trans, ser. 2, vol. iii. (1849). 



t " Ueber Bau und die systematische Stellung der Radertliiere," 

 Zeitschr. f. wiss. Zool. vi. 1855, p. 98. 



% Zeitschr. f. wiss. Zool. vii. (1855), pp. 431-436. 



