OF HETEROGENESIS 227 



organisms, accounts for the fact that the organisms grow very little, 

 and display only comparatively slight differences in size — as the 

 figures will show. 



I have seen this kind of change occur in recently cut cells as 

 well as in entire cells. And when it occurs in cut cells, it some- 

 times gradually spreads from the open extremity inwards ; but just 

 as frequently I have seen it begin at the inner and closed extremity 

 of a cut cell and gradually spread outwards. 



Some illustrations will now help the reader more fully to realise 

 what I have been describing ; but, as photographs can only show 

 the crude results rather than the minute details of this process, it 

 seemed best to reserve them till the description of what occurs 

 has been given. 



In Fig. 43 ( X 150) a portion of a cell of N. opaca crammed with 

 recently formed Actinophrys, together with partially decolourised 

 chlorophyll corpuscles and masses of motionless Bacteria, is shown 

 under a low power. Many of the specimens of Actinophrys still 

 contained green granules in their interior, though others were 

 completely decolourised. 



In N. opaca the chlorophyll corpuscles are always much larger 

 than in either of the other two species, and when they are filled 

 with large starch scales they undergo a further notable enlarge- 

 ment, as was the case in the cell from which Fig. 44, A ( x 375) was 

 taken. This figure shows an intimate mixture of enlarged chloro- 

 phyll corpuscles packed with starch scales, and embryo specimens 

 of Actinophrys, partly decolourised, into which other of the cor- 

 puscles have become converted. All stages between the two were 

 to be seen in this specimen. They were all motionless and the 

 photograph was taken without the use of any lethal reagent. All 

 that was to be seen on the surface was an accumulation of Bac- 

 teria and Leptothrix.' In B (x 200) a portion of a completely 

 decolourised cell of N. translucens is shown crammed with colour- 

 less specimens of Actinophrys, Being more developed, these 

 organisms are liable to exhibit slight though scarcely perceptible 

 movements, so that a weak solution of formalin was used before 

 the photograph was taken. Bearing in mind the small size of the 

 chlorophyll corpuscles in N. translucens it will be noted that, where 

 they are small, the specimens of Actinophrys are similarly small. 



' The surface of the cells represented in Figs. 43, 44, B, and 45, A were even 

 almost free from such organisms ; and showed not the least indication of 

 Amoebae or Actinophrys penetrating from without. 



