Experiments on metamorphosis 59 
with internal secretion (production of tyrosinase [Dewitz]?). 
Other parts of the nervous system exert no influence whatever on 
the general process of metamorphosis. 
The stimulus which is active in the transformation influences 
the processes only in the case in which the organism has attained 
a certain well-defined state of development in which it is physio¬ 
logically prepared to answer the inducement. The sexual glands 
transplanted from young caterpillars into grown up ones are going 
through the process of evolution at their own rate without being 
influenced by the new surroundings which become transformed 
much earlier. 
A few days before the metamorphosis into the chrysalis-form, 
the influence of the brain is sufficient for the transformation of the 
animal into the pupa, or for the development into the adult insect, 
even after the removal of the brain. The removal of the brain, on 
the 10 th day after the 5 th (last) moult of the female caterpillars, 
does not affect any more the behaviour of the animal with respect 
to metamorphosis. The tissues affected by the brain undergo inde¬ 
pendently further metamorphosis. The organs of adult larvae (the 
buds of the wings) grafted into young individuals continue to de¬ 
velop at normal rate although metamorphotic processes in the body 
of the host are not going on. 
By making strong ligatures in different parts of the larval body 
and cutting off the body beyond the ligature, we can produce frag¬ 
ments of the larval body, composed of any quantit} 7 of fore segments 
which are capable of metamorphosis, provided they are not lost from 
exhaustion. Analogical fragments from the posterior or middle seg¬ 
ments are not transformed into the chrysalis, except if they are 
derived from a caterpillar whose brain had already induced histo- 
lytical processes. 
If we prepare in a suitable manner two fragments of the same 
caterpillar, the influence of the brain may be made still better con¬ 
spicuous. The fragments from the anterior segments of the larval 
female body, taken a few days after the last moult, transformed 
to the pupa after 7—9 days, while posterior fragments of the same 
animals lived for 30—35 days without attaining the chrysalis-stage. 
6) The larval malpighian tubes are transformed to the tubes of 
the imago independently of the intestine and of the exertion of the 
specific function. 
