176 THE AMERICAN NATURALIST, [Vor. XXXIV. 
limits of regeneration have been found by such experiments to 
be not much less than one-sixteenth of the bulk of the original 
animal. That a much lower limit has not been found is due 
partly to the extensive exposure of internal tissues along the 
cut surfaces, and partly (perhaps) to limitation of variety of 
tissue, but certainly not, it would appear, to deficient size. 
Do all organs suffer equally in the reduction? It might be 
expected that the organs of reproduction would suffer first, as 
they do not contribute to the life of the individual; but the 
specimens used in the experiments were not sexually mature, 
so this point was not settled. The other systems of organs 
were reduced in apparently similar proportions. Thus the 
intestinal diverticula in 5 were reduced to five on each side, 
and the branches of the longitudinal nerves were apparently 
equally reduced. 
Does the reduction affect chiefly the size or the number of 
the cells? A careful histological study would be necessary to 
answer this question in detail. Not having made this, all that 
I can say is that the branched pigment cells lying near the 
surface, that are readily visible under a low magnification, are 
reduced to very few, but their size is not noticeably affected. 
Do the processes of reduction retrace the steps of normal 
growth and development? I think that this question must 
be answered in the affirmative. Certain it is that specimens 
reduced by starvation to a smaller size than just hatched 
specimens of the same species resemble these in their general 
proportions, the relatively greater breadth in proportion to 
length as compared with mature specimens, the smallness of 
the cephalic lobes, and in the small number of the intestinal 
diverticula and branches of the longitudinal nerves. It would 
be interesting to determine whether or not these artificial 
embryos, as they might be termed, could under favorable cir- 
cumstances repeat the steps to the mature and fully grown 
condition from which they were reduced. I see no reason to 
doubt that this is possible. 
In regeneration, under the circumstances of these experi- 
ments, two processes are taking place side by side; not only is 
new tissue being formed at the cut end, but the old tissues are 
