1915] LOEB—REGENERATION . 275 
SAcHS assumed that specific organ-forming substances were 
needed for growth, and that the consumption of these substances 
in the growing regions was the cause of the inhibition of growth in 
the dormant buds of a plant. While the first half of the theory may 
be correct, the second part is not tenable, since in each stem of a 
Bryophyllum there is enough “formative” material to allow each 
bud in all the nodes to grow out, while as a matter of fact only the 
most apical ones will do so. This is intelligible on the assumption 
that these apical nodes retain the “formative” material in excess of 
what they need for their own growth. 
The ideas expressed in this paper agree in the main with the 
results and conclusion of the author’s older experiments on regenera- 
tion in animals. The writer had found that if a piece be cut out 
from a stem of a Tubularia a new polyp may form at each end of 
the stem, but that the formation of the polyp at the oral end pre- 
cedes that at the aboral end; and the difference in time may be 
from one or two days to as many weeks, according to the species or 
the temperature. He found also that the formation of the oral 
polyp is the cause of the delay in the formation of the aboral 
polyp, and that if he prevented the formation of the oral polyp 
this delay in the formation of the aboral polyp was no longer 
observed.?’ This is the same rule which we have found for the 
relation between the growth of the bud of the stem and the 
formation of adventitious roots and shoots in the opposite leaf of 
Bryophyllum. The growth of this bud causes a delay in the 
growth of adventitious roots and shoots in the opposite leaf, and 
this delay is suppressed or diminished if the bud is prevented 
from growing. 
The writer suggested that a flow of substances was the cause of 
these phenomena of correlation in Tubularia. He had found that 
pigmented cells which come from the entoderm and are carried 
in the circulation are always collected at the spot where regenera- 
tion of the natural growth of the hydroid is to start. ee 
These remarks may suffice to indicate that the rules of inhibition 
observed in Bryophyllum may have a wider application. 
Logs, J., U hung physiologischen Morphologie der Tiere. T and II. 
Wiirzburg. 1890 and 1891; Pfliiger’s Archiv 102152. 1904. 
