1340 
long algae even without cleaning the glasses regularly. More remarkable 
still is that different mould-mycelia, (otherwise invariably destroying 
a culture within a short time), do not at all affect the health of 
Daphniae and do not interfere with their rapid reproduction in the 
adrenal-cortex cultures where the moulds are speedily developed. 
I have availed myself of the above phenomenon in keeping my 
insufficiently cleaned cultures alive during the holidays. Such a 
densely populated culture, which contains per 25 c.c. of ditchwater, 
say, 5 mgrms of dried adrenal cortex, mocks at all the care gen- 
erally bestowed upon an organism like Daphnia pulex, which needs 
much oxygen and is otherwise greatly affected by impurity and 
thrives best when transmitted to fresh ditchwater every week. 
The fresh adrenal cortex of the ox was carefully separated from 
the medulla, minced up, dried for 24 hrs in an incubator at a tem- 
perature of 60° and then pulverized. By due caution one really 
succeeds in getting cortex tissue free from the medulla. 
Moreover an admixture of a minimal quantity of medulla gives 
a pink colouration of the ditchwater *), so that any contamination 
may be directly recognized. 
Besides it has appeared that the medulla (if sufficiently free from 
cortex tissue)*) lacks the influence upon Daphniae described above 
and its prolongated action even seems often to be noxious. 
The quantity of dried adrenal cortex, just giving a positive result, 
amounted to 1 mgr. per 20 cc. of ditchwater. No experiments were 
made with smaller quanta. 
When we distribute sisters from the same brood over culture- 
glasses to which respectively an equal quantum of fresh aqueous 
extract ®) of dried adrenal cortex, adrenal medulla, thyroid gland 
and hypophysis of the ox is added, the medulla appears to have 
the least favourable effect. Thyroid-gland extract is often tolerated 
less in the beginning than after prolonged administration (tachycardia), 
the reproduction of Daphniae is much less intensive than in the 
adrenal cortex cultures, stronger though than in the control-cultures, 
and the same holds for the hypophysis-cultures. 
The extremely rapid growth of algae in the culture-glasses to 
which adrenal-corter is added, is very striking. By placing the 
1) This is a very sensitive adrenalin-reaction, appearing in the presence of oxygen 
(Bied] I, p. 527). 
2) It is much more difficult to obtain adrenal medulla free from cortex-tissue 
than vice versa. 
3) 1 ee. of aqueous extract (prepared 24 hrs previously by adding 0,5 gr. to 
25 c.c. of water at room-temperature was added to 10 c.c. of ditchwater. 
