ORGANIZATION AND GROWTH 221 
associated with this contraction stimulates the neighboring 
nerves or muscles, thus causing the latter to contract. In 
this way a conduction of stimuli is brought about without the 
presence of a central nervous system, the effect of which is 
the same as when a central nervous system is present. There 
is so little difference between the latent period of stimulation 
and the time the body remains contracted after the stimula- 
tion, in the normal and in the brainless animal, that it can- 
not be determined by mere observation unaided by special 
apparatus. 
What occurs here in the entire animal happens in a lim- 
ited portion of an earthworm when it is cut across trans- 
versely and the two pieces are sewed together. As Benedikt 
Friedlander has shown, both pieces are still able to perform 
co-ordinated movements of locomotion." I have repeated 
the experiments of Friedlander upon leeches, and have 
observed the same series of phenomena in them. 
Two years ago I made some observations upon a marine 
Planarian, Thysanozoon brocchii, which are similar in cer- 
tain respects to those upon Ciona, into a discussion of which, 
however, I cannot enter here.’ 
4, Since I had received the impression that Ciona is helio- 
tropic, I tried to see whether a Ciona robbed of its nervous 
system would also react to light by heliotropic bendings. 
The object of my experiments was thwarted by an unwished 
for, but perhaps interesting, result. In the course of four 
weeks all the animals (which had not died) had regenerated 
a new brain. I repeated the experiment, because I did 
not believe my first results. But I can no longer doubt 
1RBENEDIET FRIEDLANDER, Biologisches Centralbl., Vol. VIII (1889). 
2The Darwinians would probably call the reaction of a Ciona intestinalis to 
contact the consequence of a ‘ protective instinct.” These “ protective instincts,” 
so far as I can see, are said to consist in this, that the animal has by natural selec- 
tion acquired, in the course of the customary million years, certain cerebral con- 
trivances which are now inherited from one generation to another. But in the case 
of Ciona these hereditary “instincts” cannot well be located in any special portion 
of the brain, for they continue to exist after the removal of this organ. 
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