OF CILIATED INFUSORIA 277 



As to the reality of this transformation there is, in fact, absolutely 

 no room for doubt. There are only two possible sources of error : 

 (i) the mistaking encysted Otostomas for Hydatina eggs, and (2) 

 the risk of ' infection.' 



The first possibility, which was scarcely worth mentioning in 

 connection with any competent observer, has been completely 

 dissipated by the discoveiy of the great bulk and the thick cyst 

 of the mature encysted Otostoma, together with the recognition 

 that the product emerging from the egg-case, notwithstanding its 

 size, is only an embryo ; while the second possible source of error 

 is shown to be equally untenable, because if a germ of the Otostoma 

 existed which could penetrate the Hydatina egg and could devour 

 its contents, any such young Ciliate should be visible during the 

 process — if not at first, certainly when and after it had devoured 

 one-half of the contents of the egg. But no young Ciliate devouring 

 its contents can ever be seen within the egg-case. On the contrary, the 

 photographs show a peculiar and definite set of changes taking 

 place throughout the whole substance of the egg, and, as a sequel, 

 the entire contents revolving in the form of a great embryo 

 Ciliate. 



(2) The Origin of 12 to 20 Vorticellce or Oxytrichce from the substance 

 of a single Hydatina egg. 



These are most i-emarkable variations, which at different times 

 have been occasionally met with in Hydatina eggs taken from the 

 experimental vessels. Both of these changes have only been met 

 with in eggs found at the surface of the fluid in the experimental 

 vessels ; while the transformation of the egg-mass into an Otostoma 

 seems to occur more abundantly, away from the air, in eggs which 

 drop to the bottom of the pots. The changes into Oxytrichse have 

 been met with in the spring on three separate occasions ; those 

 into Vorticellae only once, and that in the autumn. 



The first occasion on which the transformation of the Hydatina 

 egg-substance into Oxytrichae was met with was in 1872, and is 

 thus referred to in " The Beginnings of Life " (vol. ii., p. 489) : — 

 " The substance of some of the large thin- walled ' eggs ' of 

 Hydatina senta was seen to have undergone segmentation into 

 about 16 spheres, each i/iooo" in diameter. The external layers 

 of these soon became condensed into cyst- walls, whilst the internal 

 substance of each of them, after undergoing a series of molecular 

 changes, resolved itself into an embryo Oxytricha, some of which 



