612 Sergius Morgulis 
When, however, the worms of these two groups are allowed to 
regenerate for a longer time, we find a rather interesting condition. 
In the first place, it will be found that the retarding effect pro- 
duced by the second operation wears off in the course of time, 
and the worms regenerate again at a nearly normal rate. More- 
over, it will be observed that the ones which had regenerated 
the smaller number of segments before the second operation was 
executed required a shorter time to regain the normal rate of 
regeneration than those which had regenerated a larger number 
of new segments when operated on the second time. From Tables 
VI and VII it will be seen that while the worms of the ‘first set 
(Table VI), at the end of about eighteen days, regenerate at 
a nearly normal rate, those of the second set (Table VII) are still 
under the influence of the second operation and regenerate (on 
an average) a smaller number of segments than normally. 
It will also be seen from Table VII, that while after the first 
operation from 3 to 8 new segments had been regenerated by 
the end of twelve days, after the second operation even during a 
period one and one-half times longer the same worms had regen- 
erated only 5 to 6 new segments. 
It would be interesting to determine by special experiment 
the relation that exists between the period at which the second 
operation is performed and the immediate effect of the operation 
upon the rate of regeneration, as well as the after-effect of the 
operation. 
V RELATION BETWEEN FOOD-SUPPLY AND RATE OF REGENERATION 
The réle of food in regeneration is commonly supposed to be 
of slight or of no importance, but the following experiments will 
show that such an attitude toward this factor is not warranted. 
There are on record some unquestionable cases, in which no 
definite relation between food-supply and regeneration could be 
found; as, for instance, that of the splendid experiments of 
McCallum (’05) with plants, from which he arrived at the con- 
clusion that ‘‘there need be no increase in nutritive conditions » 
