2 20 
J. Bretland Farmer . 
preservation of individuals possessing and retaining such mechanism 
in good working order. 
I have mentioned galls as due to functional disturbances, that is 
to the existence of special relations between stimuli not normally 
met with in the proper limits of the plant-body and its responsive 
machinery, whereby outgrowths having a definite form, due as 
I believe to the composition of their material substratum, are 
produced. And similar derangements are not unknown, though 
their causes are more obscure in animals. Tumours, and especially 
the malignant growths of cancer, are due to causes that unduly 
stimulate particular layers of tissue to excessive development, 
whereby they may proliferate and invade other parts of the body. 
Although at present the causes of cancer are obscure, we are very 
sure that if we can track the stimulating agency to its source, the 
secrets of the etiology of the disease will be revealed. 
Allied to the problems presented by the facts of co-ordination 
are those involved in the processes of regeneration and healing of 
wounds. As regards the latter, a response to the action of the 
surrounding medium on the part of the protoplasmic body is a 
condition of its existence, and a lack of response would rapidly 
ensure the extinction of so imperfect a mechanism. It seems to he 
often thought, in the case of animals, that the inner organs of hypo- 
blastic origin are less susceptible to reparation than those 
originating from the outer embryonic layers. May not this be an 
example of lack of response, because during the changes that have 
occurred in the gradually revolving organization, this property 
became less important as a criterion of the safety of the organism 
inasmuch as the tissues in question were less likely to receive those 
stimuli due to lesion P 1 
It is the power of suitably responding to stimuli that in the 
long run determines the survival or extinction of a species, but the 
suitability or the reverse of the response is an accident of the 
mechanism as a working structure, and primarily is entirely inde¬ 
pendent of the causes to which the genesis of the mechanism itself 
is due. It is an out come of organisation, but in no sense the cause 
of it. The remarkable results obtained on extirpating the stalked 
eye of certain decapod crustaceans, whereby either an antenna-like 
structure or another eye may alternatively replace the lost part, 
according to whether the ganglion has been removed or not, 
emphasises this aspect of the matter. 
’I do not attach much importance to this interpretation, and 
indeed the statement itself has been challenged, 
