NOTE X (p. 31).
The normally-fed fly larvae required just as much time for their development into the adult form as those that were poorly fed—namely 206 hours; and they fed almost continually during the whole time. The ill-fed larvae were only allowed to feed for 138–150 hours, i.e. six-tenths to seven-tenths of the normal time. But these figures express the difference in the feeding of the two lots very imperfectly: the difference was, in fact, much greater, as is evident from the fact that the ill-fed larvae grew much more slowly and remained much smaller than the others. We may therefore say that at any stage in the 138–150 hours of their larval life they were less capable of taking nourishment than they would have been had they been of normal size on reaching this stage.
NOTE XI (p. 35).
I formerly indicated, not without good reason, that the eggs break down to help in sustaining the animal: this is at any rate the result of their disintegration, though perhaps it is simply an unavoidable and not an intentional one. The flies already referred to furnished another proof as to the extent in which the maturation of egg-cells depends on food. I had begun my experiments by endeavouring to find out whether the flies would reproduce at all in confinement: this could not be predicted of them, for many insects—butterflies, for instance—in general do not do so. And, in fact, it seemed at first as if the same would be true in this case also; for, in spite of abundant feeding with carrots and sugar, more than a month passed without any eggs being produced. As soon, however, as I introduced some meat into the case containing flies, they all darted down upon it, and greedily sucked its juice. In their craving for flesh they crowded on to the piece; and the result was that in a week afterwards a great number of eggs were laid. The quantity of nitrogenous food had therefore been too small, and without it the eggs could
