MICROSCOPY. 699 
doned the doubts raised by Ehrenberg and others, and believe in 
the revivification of rotifers, tardigrades, etc., after complete and 
unlimited desiccation. His own experience with a colony of roti- 
fers which he received by post in a few grains of dry, dusty pow- 
der, and almost immediately brought to life by watering it in a 
stage-tank, was suggestive, certainly, of wonderful powers of en- 
durance. He narrates the history of this colony as follows :— 
*¢ Since its establishment in 1867, it has received no new immi- 
grants, but as it increased and multiplied, some of its members, in 
a dry state, have been removed to stock new tanks for my friends. 
It is generally kept in a cabinet, with other objects, and watered 
or examination when required, or, as a rule, once a month ; so 
small a quantity of water dries up rapidly in summer; in a day 
sometimes. The longest time it has kept continuously dry is ten 
months; in winter, after watering, it has been frozen into a mass 
of ice; it has been heated ona brass mounting-table, "with a spirit 
a sea voyage to the south of Spain, revived there - brought 
home again; taken to Ceylon; to India; revived on ship-board, 
to the astonishment of the passengers; brought Faiy and a few 
of the dry inhabitants immediately posted off again to a friend in 
Ceylon, who revived and has them still. As a final indignity and 
injury this much enduring family has been put into the receiver of 
an air-pump for twelve hours and thorou hly exhausted. This 
was almost too much for it, but still there is a little life in the 
tank.” 
Experimenting on this subject, he found that, while some could 
survive a short exposure to a heat of 200° (Fahr.), a thorough bak- 
ing or boiling for two or three hours killed them all. Drying for 
a week in an exhausted receiver along with sulphuric acid was 
also fatal. He admits proof of revival after four years’ torpor ; 
though he failed in experiments extending over only from one to 
three years. Though nearly all authorities agree in the books as 
to the desiccation theory, yet many good observers privately doubt 
whether those that revive were really dried at all; and Mr. Davis 
is satisfied that the non-revivers are the dried ones, and those 
which revive do so because they were not desiccated. He has ob- 
served that the creatures constantly give off a slimy secretion ; and 
in drying they contract into an ovoid form, and the gelatinous fluid 
dries over them into a thin hard shell which protects them from 
further drying. If isolated rotifers are dried upon a clean glass 
