POLTGASTKIA. 



33 



lie free in a clearly defined cavity of the body, which opens by a 

 narrow canal through a projecting portion of integument, upon 

 an infundibular orifice with a labiated border. Cohn saw these 

 germs escape by this canal and orifice, the canal expanding, and 

 the germ yielding to the pressure and becoming a narrower and 

 longer body in transitu (yfig. 18, e ). The parturition lasted twenty 

 minutes, giving ample time to observe and delineate a germ half 

 in and half out of the mother. As soon as one end of the germ 

 enters the surrounding water, it begins to ciliate and create a cur- 

 rent, which accelerates the birth : this completed, the young rests 

 awhile beside the mother, then separates itself and moves freely 

 through the water. It is cylindrical, thrice as long as broad, obtuse 

 at both ends : but the embryos vary in size from y^'" to -=^'" in 

 length. They are colourless, sometimes present little tubercles at one 

 end, have no mouth, are beset by fine and long cilia, and differ so 

 much from' the parent that their relationship could not be recog- 

 nised without observation of the birth. They have accordingly been 

 referred, to a distinct genus, viz. Cyclidium, by Ehrenberg. * As soon 



as one germ is bom, 

 out follows another; and 

 Cohn thinks that when 

 only one or two are 

 seen in a Loxodes, the 

 rest have already es- 

 caped ; and that many 

 are developed as a rule. 

 The position of the 

 outlet varies ; and Cohn 

 once saw two embryos 

 escaping by two distinct 

 apertures, which indi- 

 cates that the 'vulva' like the 'anus' may be casual and temporary. 

 The pulsatile vesicles of the parent are not disturbed in their actions 

 during the parturition. The rotation of the chlorophyl-cells is arrested 

 so long as a germ is inclosed in the body : but it is resumed, and goes 

 on more rapidly, as soon as the parent is relieved of her burden. One 

 of the moieties of a longitudinally splitting Loxodes may sometimes 

 be seen to contain germs, and these also to be excluded even before 

 the other moiety has become separated : thus the two distinct gene- 

 rative processes may go on simultaneously. 



* Cydidium margariiaceum, XL p. 387., pL y^ii 

 D 



