448 M. Eckhard on the Organization 



worms, and which consists in this, that in the interior of the 

 parent animals, germs (which had not hitherto been shown to be 

 a consequence of sexual influences) are formed and separated. 

 The fact which I have stated, that I have seen these globules 

 escape, appears to support this view. 



We have as yet been purposely silent on the true organs of 

 generation, so as to be able now to devote ourselves to their con- 

 sideration alone. Ehrenberg has mentioned as sexual organs 

 one or two contractile vesicles and glands occurring either singly 

 or in considerable number *. I shall consider both minutely, 

 and see what signification they admit of. 



A. The contractile vesicle. — If we examine a Stylonychia (PL IX. 

 fig. 2) or a Bursaria, we observe, with a little effort, a bright, 

 tolerably large vesicle. At first sight it appears to be a round 

 aperture in the skin, whence it has happened that many observers 

 have considered it as having some relation to the respiration ; 

 this however is by no means the case, for it lies within the body. 

 We may easily convince ourselves of this fact by observing the 

 animals (as Ehrenberg first stated) whilst revolving on their 

 longitudinal axis. At those moments when the vesicle disap- 

 pears, we see distinctly how the lines which cover the whole body 

 longitudinally and are covered with cilia are drawn over the spot 

 which is apparently open. It is often difficult to discover the 

 vesicle on account of the number of granules which exist in the 

 skin. The most common and very constant form is the globular ; 

 we scarcely ever notice any form which differs materially from 

 this. But in some genera radii occur which traverse the body 

 in a stellate manner, and are sometimes longer, at others shorter 

 (fig. 4) . The varieties in the number of the vesicles are likewise 

 slight ; there are usually one (in most genera) or two (Parame- 

 cium, Chilodon Cucullulus) . Sometimes indeed several occur, but 

 then usually the animal is in the act of division. In § 17 of 

 Siebold's work there is something to correct. According to his 

 account, Trachelitis Meleagris is covered with a row of from eight to 

 twelve round contractile cavities (p. 21) ; and Ehrenberg regards 

 the colourless juice they contain, in consequence of an optical 

 illusion, as gastric cells filled with a reddish gastric juice. But 

 the fact is this : the eight to twelve round vesicles do not appear 

 red as the result of an optical illusion, but in consequence of the 

 coloured juice contained in them ; for when the animals dissolve, 

 the red juice is seen to pour out. This animal also exhibits two 

 other vesicles, which are the true contractile bladders. Those oc- 

 curring also in Amphileptus Meleagris and longicollis appear to me 

 to correspond to the eight to ten vesicles in Trachelius Meleagris, as 



* On a double condition of the sexes demonstrable as far down as the 

 Monadina. 



