1885. ] Zoölogy. 717 
ZOOLOGY. 
INDESTRUCTIBLE ĪNFUSORIAL LIFE.—)]. Hogg describes some 
further experiments he has made on this subject, supplementing 
those previously recorded on rotifers. Some Ciliata and Tardi- 
grada have been included, and these have, although not to the 
same degree, exhibited a remarkable tenacity of life. The inter- 
vals of sleep and vigorous life have also been brought into 
strict accord with the durations of dry and wet periods of the 
year, so that the subjects of the experiments have been kept in a 
perfectly dry condition during the whole of the long drought 
which characterized the past summer. 
Moreover, some older dried specimens were subjected to an ar- 
tificial process of desiccation. They were kept for a time in a hot- 
air chamber, the heat in which was raised to 2000 F., and subse- 
quently the miniature aquarium in which they were inclosed was 
plunged into a freezing mixture. Neither process kille@them nor 
greatly diminished their vital powers, their revivification in both 
ases being somewhat delayed. Certain poisons known to exert a 
baneful influence over higher animals were added to the water 
supplied to the rotifers, but in no way did they produce discomfort ; 
on the contrary, portions were taken into the stomach and partly 
digested. On the other hand,a drop of sewage water caused 
marked discomfort ; they immediately retracted their rotating or- 
gans and sank to the bottom of the cell. These were, so far as could 
be ascertained, poisoned, and this was probable owing to the free 
sulphide of hydrogen evolved by the putrescent sewage. From 
VOL. XIX.—NO. VII. 47 
