82 GENERAL HISTOEY OF 



In the immature and young state of Eudorina, of Melicerta ringm», 

 and of MegalotrocTia alba, &c., distinct eyes are present, wliicli, how- 

 ever, disappear vnih. advancing age. 



The sense of touch diffused generally over the body, is especially 

 concentrated in the rotary organ, and in the styliform processes or 

 comua, so frequently produced from it, which may be deemed analo- 

 gous to the feelers {aniennce) of insects. We may presume also that 

 the toe-like processes of the foot or tail are more largely endowed 

 with sensibility. 



Mr. Gosse describing the AsplancJina priodonta, writes : " Each of 

 the three eyes rests on a mass that appears ganglionic ; the clubbed 

 masses at the lateral apertures are probably of the same character ; 

 and the interior of the body contains a number of very delicate 

 threads, floating fi-eely in the contained fluid, which have thickened 

 knobs here and there, especially where they anastomose (see fig .") 



Section XXIV. — Of ihe reproductive organs, and the reproduction 

 of Rotatoria. — The only method of propagation of Rotatoria is by 

 ova, of which they deposit only a few at a time. The size of the 

 egg is about l-36th that of the parent, and the young of those in 

 which incubation is completed before expulsion is sometimes two-thii'ds. 



Although the Eotatorial Infusoria are not endowed with the 

 various faculties of reproduction possessed by the Polygastrica, yet 

 their vast increase by eggs only, would astonish most persons who 

 have not considered this subject. Ehrenberg informs us that he in- 

 sulated a single specimen of Uydatina senta, and kept it in a separate 

 vessel for eighteen days, that during this interval it laid four eggs 

 per day, and that these yoimg, at two days old, lay a Uke number, so 

 that, when circumstances are favoui'able, one million indi^-iduals are 

 obtained from one specimen in ten days ; that, on the eleventh day, 

 this brood will amount to four millions, and on the twelfth day to 

 sixteen millions. Although the fecundity of this Rotatoria is the 

 greatest that has been tested by direct experiment, yet (says 

 Ehrenberg) in the large Polygastrica, as the Paramecium aurelia, a 

 single specimen in one day increases to eight, by simple transverse 

 division of the body only ; so that, if we take into this account the 

 other modes of the increase of this creatui'c, namely, by eggs, often 

 in masses like the spa\vn of fish, and again by buds growing from 



