OF CILIATED INFUSORIA 283 



photograph these last, I unfortunately pressed upon the cover- 

 glass, and thus displaced and damaged the specimens. I could 

 therefore only photograph the best of the damaged specimens, as 

 it is to be seen in D ( x 250). It contained one active Oxytricha 

 (on the left) and four matrices, though two of the latter, as shown, 

 are much out of focus. In one of the large eggs also, four active 

 and larger Oxytrichag were found, such as are shown in B (x 250), 

 after the specimens had been altered in appearance by the weak 

 iodine solution used to stop their movements. 



Apart from the great Otostomata, only Vorticellas or Oxytrichas 

 have ever been seen by me within the unruptured egg-cases of 

 Hydatinae, though, as I have indicated, on two other occasions I 

 have seen as many as from 15 to 20 of the smaller Aspidiscse partly 

 filling ruptured egg-cases (note, p. 279). It is quite possible, there- 

 fore, that these last may also have taken origin, like the Vorticellas 

 and the Oxytrichas, from the substance of the Hydatina egg. Such 

 an egg as that shown in Fig. 77, A (several of which I have seen), 

 whose spheres are distinctly smaller than those shown in Fig. 76, D, 

 might yield such very small Aspidiscas as were found in the egg- 

 cases above referred to. These small spheres are larger than the 

 ordinary vesicles that are produced, and which become welded 

 together into one mass, during the production of an Otostoma. 

 Eggs of this latter type are shown in different stages in Fig. 75, 

 for comparison with the kind of change that leads to the formation 

 of the little separate spheres shown in Fig. 76, D — from which 

 embryo Vorticellas or Oxytrichae are presumed to take origin. 



It is certainly a fact of great significance that, of all the extremely 

 varied kinds of Ciliata, it should be precisely these three forms 

 found by me within the Hydatina egg-cases that were demon- 

 strated over fifty years ago, by independent observers (Pineau and 

 J. Haime), to be convertible forms of life — to be, therefore, in a 

 sense, analogues of those crystals whose forms and colours change 

 under varying conditions, as a result of isomeric molecular re- 

 arrangements, of a kind similar to those that I have been 

 postulating as causes of heterogenetic transformations (see 

 pp. 44-47). 



There seems absolutely no room for doubt that the Vorticellae 

 and the Oxytrichas found in numbers within unruptured Hydatina 

 egg-cases have been produced from the very substance of the eggs 

 by the intervention of such changes as are indicated in Figs. 76 



