254 HETEROGENETIC ORIGIN 



derived from a transformation of the egg of a Rotifer (Hydatina). 

 Recognising its condition I made only a hasty examination, and 

 abstained from taking a photograph at a higher power than 

 150 diameters, in order to avoid the chance of interfering, by a 

 more prolonged exposure to the light of the lamp, with the 

 progress of changes that seemed to be taking place in the eggs. 

 I much regretted this at the time, epecially because of the appear- 

 ance of the anterior of the four eggs, in which the formation of 

 corpuscles, such as are found in the Ciliates, appeared to be going 

 on, though in their ordinary condition the eggs of the ' Sloth ' are, 

 like those of Hydatina, simply granular. On examination after 

 twenty-four hours, I again found that a complete metamorphosis 

 had taken place ; the four eggs were gone, and with them all that 

 was within the integument of the Macrobiotus, including the 

 whole of its scattered pigmentary lining, and in their place were 

 found about twenty very active red-brown Ciliates of different 

 sizes, such as are shown in Fig. 55, C (x 150), after they had been 

 killed by a weak osmic acid solution. The bodies of most of them 

 were filled with the usual great corpuscles ; some of them were 

 distinctly pyriform in shape, and cilia were principally seen 

 about the narrow anterior extremity — indicative of their embryonic 

 character. A portion of this ' Sloth,' more highly magnified, 

 is to be seen in D (x 250), which shows the great corpuscles 

 within some of the Ciliates, and the pyriform shape of others. 



Looking to the previously altered shape and appearance of 

 the eggs, as shown in B, and to what was found only twenty-four 

 hours later in C, the most feasible explanation of this transforma- 

 tion, after all that I had previously seen and some other things 

 that will be described in the present chapter, :s (a) that the eggs 

 had been converted into great Ciliates ; and that subsequently 

 two processes went on, (&) the gradual devouring by these 

 creatures of the body substance of the parent organism, and 

 (c) the multiplication by fission of the Ciliates, as they gorged 

 and grew. 



Happily a more recent observation has enabled me to prove 

 the actual occurrence of the first of these processes — namely, the 

 conversion of the egg of the ' Sloth ' into a single great Ciliate. 

 The following details and illustrations will make this clear. 



On May 9, a rather large Macrobiotus, with five large eggs, was 

 found dead beneath a cover-glass, though it had been seen alive 

 and with the same number of eggs, only twenty-four hours 



