260 HETEROGENETIC OEIGIN 



large motionless bodies otherwise similar to the Ciliates is shown, 

 such as may also be seen near the centre of Fig. 57. Although 

 this particular body was motionless, others, just as large, have been 

 seen slowly moving by means of a few short, languidly-playing 

 cilia. This body possessed a very large, finely granular nucleus, 

 like that in the egg : proportionately larger, it is true, and other- 

 wise differing in appearance from the one being unstained and the 

 other stained. But exactly similar very large nuclei are to be 

 seen in the smaller Ciliates shown in Fig. 60, A, B (x 375), also 

 stained by a weak solution of iodine, which were moving slowly 

 by very short delicate cilia, such as are dimly indicated in the 

 figures. Some of these smaller bodies were motionless ; while 

 others were seen slowly revolving within a most delicate hyaline 

 cyst. This was the condition of the two bodies that are shown 

 outside the abdomen of the fly in Fig. 58. The application of the 

 iodine solution caused rather wild movements for a moment, which 

 dilated the cysts. These are still faintly indicated in the figure — 

 that around the lower of the two Ciliates being the more distinct. 

 Within the portion of the abdomen shown in the figure seven 

 other and rather larger Ciliates, with great nuclei, are represented. 



The large body shown in Fig. 59, B, is, I believe, an encysted 

 matrix, destined to develop cilia and to undergo fission after 

 emerging from its hyaline cyst, so as to produce such smaller 

 embryo Ciliates as are shown in Fig. 60, A and B. That they are 

 truly embryos, beginning their active life as bodies of this size, 

 is confirmed by the following facts. 



Some of these Ciliates have been kept alive on two or three 

 occasions in dilute egg emulsion for twenty-four hours, and by 

 that time these extremely delicate bodies had undergone a very 

 distinct development. Their investing membrane had become 

 firmer, and the cilia larger and much more numerous, as shown 

 in Fig. 60, C (x 375) ; while the bodies of the Infusoria had become 

 densely packed with granular matter, which almost completely hid 

 the nucleus. In some of them, as in this particular specimen, 

 a sluggish contractile vesicle was seen, but I have not been able 

 to recognise the mouth in any of them. Their movements of 

 translation were rapid, and associated with partial rotations of 

 the body. On two separate occasions, when they have been kept 

 alive for twenty-four hours, I have found large numbers of them 

 with short abortive cilia and in a state of partial division, as 

 shown in D ( X 375) ; though, strangely enough, in none of them 



