390 Prof. H. C. Bastian. On the Occurrence of certain [Feb. 14, 
found to be much larger, having from two to three times the length of the 
great embryos which issue from the egg-cases; and also to be more highly 
organised, seeing that what appeared to be a simple contractile vesicle has 
only once been seen in one of these embryo forms, while it is always 
present in a developed form, in association with 10 to 12 spindle-shaped 
radiating channels, in the adult specimens. A starved specimen of one of 
these Otostomata, leading a free life, showing the small ear-like mouth and 
the large nucleus, is shown in fig. 10. 
Many of these adult specimens I have been able to keep for two months, 
and have seen them pass into an encysted condition. When in this state 
their bulk may be seen to be several times greater than that of Hydatina eggs. 
They are, likewise, enclosed in thick cyst walls, wholly unlike the thin egg- 
cases of the Hydatina. A rather small specimen in this condition is shown in 
fig. 10. 
A Hydatina egg could not possibly be confounded with an adult encysted 
Otostoma; and the embryo Otostoma which emerges from the egg-case 
embodies the whole of the transformed substance of the egg. No minute 
Otostoma ws ever to be seen within an egg, devouring\tts contents. No Ciliate is 
seen till the total contents of the egg having been transformed, the whole 
mass begins to revolve within the egg-case as a great embryo Otostoma. 
(2) The Origin of 12 to 20 Vorticelle or Oxytriche from the substance of a 
single Hydatina HEgg—These are most remarkable variations, which at 
different times have been occasionally met with in Hydatina eges taken from 
the experimental vessels. Both of these changes have only been met with in 
egos 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 Oxytriche have been met with in the spring on three 
separate occasions; those into Vorticelle only once, and that in the autumn.* 
The first occasion on which the transformation of the Hydatina egg- 
substance into Oxytrichee was met with was in 1872, and is thus referred to 
in “The Beginnings of Life ”t:—“ The substance of some of the large thin- 
walled ‘egos’ of Hydatina senta was seen to have undergone segmentation 
into about 16 spheres, each 1/1000’ in diameter. The external layers of 
* It is admitted that metamorphosis from one to another form occasionally occurs 
among the Ciliata during their stage of encystment (Carpenter on ‘The Microscope,’ 
Kighth Edition, 1901, by Dallinger, p. 780) ; and among such instances of alleged trans- 
formation it is of interest to note that the origin of Oxytriche from encysted Vorticellz 
was described and illustrated by Pineau in the ‘ Annales des Sciences Naturelles,’ 1848 
(Zool.), p. 99.—Wote added June 29, 1905. 
+ Vol. 2, p. 489. 
