990 S. J. HOLMES 
little reduction in size either of the cells or their nuclei as a 
result of starvation; the diminution in the size of the body was 
produced mainly by their reduction in number. Various organs 
suffered unequally in this process. Organs of copulation, sex 
ducts and vitellaria were among the first to disappear, the eyes 
degenerated, and there was a marked reduction in the number of 
parenchyma cells. The muscle cells suffered little decrease and 
the number of muscle bands remained unaltered; there was little 
reduction in the nervous system. The male sex cells were among 
the least altered. Cells of the intestinal epithelium and the outer 
ectoderm, while reduced in number, were not reduced dispropor- 
tionally to the body as a whole. 
The study of small regenerated planarians was undertaken in 
order to ascertain how far the various organ systems would suffer 
on account of reduction in size and how far the results might be 
parallel with the effects of starvation. Through successive regen- 
erations it is possible to carry the reduction very much farther » 
than can be done by the withdrawal of food. While starvation 
may reduce the animal to one-tenth or one-twelfth its original 
size, by the method of successive regenerations it may be reduced 
to ;ooo OF yso0 its original size. Many of these very minute 
animals had practically the same form as the adult. Several 
specimens were sectioned and careful measurements were made 
of several kinds of cells and compared with measurements of 
corresponding cells of individuals of ordinary size. Ectoderm 
cells, parenchyma cells, cells of the intestinal epithelium were of 
the same size as in the larger worms. The muscle cells, while 
less in length, were nearly as thick as in the larger worms. The 
nuclei were also not reduced in size and therefore bore the usual 
relation to the size of the cells. The gonads, sex ducts, copula- 
tory apparatus and vitellaria could not be found. The muscu- 
lar system is well developed, the outer layers being present and 
only a little thinner than in normal individuals. The number of 
dorsoventral strands in a cross-section is not more than about 
one-fourth that of larger specimens and they contain fewer 
fibers. The alimentary canal has but a very few short branches. 
The cells are not shrunken as occurs in starved individuals and 
