1341 
animals during the experiment in a badly lighted space it may be 
observed, that only the addition of the adrenal-cortex tissue is 
answerable for the favourable condition of the cultures, but „ot the 
rapid growth of the algae. It has, for that matter, already been 
stated that the growth of multicellular algae is just a factor which, 
on the contrary, inhibits the development of Daphniae. 
An aqueous extract of the dried adrenal-cortex (0,5 gr. per 25 cc), 
which had been heated for 2 hours at 110° in the autoclave, proved 
to have the same favourable influence as the non-heated extract on 
the growth of the algae. Judging from the preliminary experiences 
it also seemed to promote the reproduction of the Daphniae. Spon- 
taneous growth of moulds does not occur in these cultures, so that 
they have still to be infected in order to ascertain whether the pro- 
longed heating leaves intact the substance, wich counteracts the 
effect of moulds in the cultures. 
In the spring of the year 1920 I noted an extraordinary difference 
in the growth of eggs of the watersnail (Limnaea ovata), according as they 
were treated with dried adrenal-cortex, or not. A mass of jelly containing 
eggs, originating from a single female, has been cut in two halves, 
each of which has been put in a glass filled with ditehwater. During 
the experiment an equal amount of algae was added to each glass. 
After the lapse of three weeks the size of all the young snails, 
contained in the glass, to which a few milligrams of dried cortex 
of the suprarenal capsule had been added, surpassed several times 
the size of those of the controlculture or the adrenal medulla cultures. 
It has been shown, that the adrenal cortex contains a substance, 
soluble in water, which in these invertebrates exerts an influence 
upon their fecundity and upon their health. Factors, which are in 
other circumstances noxious to Daphniae, such as caused by over- 
population, inadequate supply of oxygen, the growth of moulds and 
of multicellular algae, are removed by the addition of very small 
quantities of dried cortex of the suprarenal gland. This influence 
seems to exist also among lower plants, witness the highly intensified 
growth of unicellular and multicellular algae. Sexual maturity is 
accelerated, the embryonal development is promoted, the broods 
follow each otber in quicker succession. In the snail the rate of 
growth of the tissues has largely increased during the embryonal 
and the post-embryonal stage. 
The study of adrenalin has pushed the question of the significance 
of the adrenal-cortex tissue into the background for a considerable 
length of time, until it was brought under our notice again, notably 
