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expect from the preceding results, the yield of spores is very 
small and often nothing. In all experiments in which the 
blocks behaved in this fashion, the blocks were rejected. 
Summing up the results thus obtained, we find that for SS. 
cerevistae— 
1. The yield of spores is directly proportional to the 
porosity of the material used for the culture block. 
2. The yield of spores is inversely proportional to the 
amount of food material present. 
3. Large quantities of CO, inhibit the spore formation; 
and the less the amount of CO, present the better the 
yield. 
4. Variations in osmotic pressure up to the amount exerted 
by 5 per cent. KNO, solution do not affect the yield. 
Ten per cent. potassium nitrate solution retards spore 
formation. 
5. The amount of moisture present does not affect the 
yield unless the eration of the cells is too greatly 
interfered with. 
For S. anomalus the conclusions are similar with the excep- 
tion of 2. In this case the yield of spores is directly propor- 
tional to the amount of food material present. 
The results, on the whole, support Hansen’s view that good 
eration is necessary for spore formation. This seems to be 
the necessary condition in all cases for both species. Klebs’ 
view apparently receives support by the behaviour of S. 
cerevisiae. But may it not be that for this and other vigorously 
fermenting species, when fermentable sugars are present in any 
considerable quantity, a large amount of CO, is produced, and 
that the presence of this gas serves to inhibit the spore forma- 
Hen? Ae any tates Klebs’ view ocunnet hold good for S. 
anomalus, and it is quite possible that the numerous other 
species which also form spores on various nutrient media may 
behave in the same way as this species. 
Il. The influence of internal conditions on spore formation. 
a. The cells must be in a vigorous state of growth. This 
is effected by twice successively cultivating the cells 
in fresh beer-wort for ag heer a tae? TCs oEhe 
necessity of this condition is easily proved by making 
spore cultures with cells of S. cerevisiae 24 hours, 48 
hours, 72 hours, &c. old. The only case in which an 
abundant spore yield is obtained js when cells 24 
hours old are used. Few spores are formed in other 
