8 4 
Review. 
evolution is a different matter. It is, as Darwin has said 1 , ‘ the most 
interesting department of natural science, and may be said to be its 
very soul/ But this is only true of evolutional morphology, which 
sees in unity of type the expression of community of descent, and 
thus throws into the study of form that vitality which before it lacked. 
A similar change has been wrought by evolution on teleology. The 
belief that each organ was formed in its present shape by the Creator 
for a certain purpose has no doubt had a stimulative effect on the 
study of function. Nevertheless the fact remains that the investiga- 
tion of the uses of the parts of living things only sprang into its present 
youthful vigour when the ‘ Origin of Species ' had rendered possible a 
new and vivid science of evolutional teleology. Thus, these two 
branches of inquiry, morphology and teleology, which had no other 
bond than such as could be gained by guesses at the will of the 
Creator, are now connected on the basis of the theory of ‘ evolution by 
means of natural selection/ We have dwelt on those considerations 
because we think that morphology, as it now exists, ‘ wedded ’ as 
Professor Asa Gray has said ‘to Teleology/ is a science capable of 
embracing physiological considerations ; and because we believe that 
it is not necessary for the physiologist to rebel against the usages of 
morphology in his search for a striking standpoint. 
In reading the first lecture we find ourselves forced to ask in what 
way Professor Sachs arrives at his physiological types. A morpho- 
logical type connects itself with the theory of descent, but on what 
basis can Sachs’s types stand ? An example will make our difficulty 
clearer. He divides the body of the more highly developed plants 
into Root and Shoot. The root being distinguished as that part which 
is developed in the substratum, and also by the absence of reproduc- 
tive organs, while the shoot is developed outside the substratum, 
‘produces and increases the substance of the plant’ and also bears 
the reproductive organs. Professor Sachs developes this idea, it is 
needless to say, with his usual skill; the result being a highly interesting 
discussion on what Professor Ray Lankester has called ‘ homoplastic ’ 
organs, i.e. such as are not homologically related, but are forced into 
a certain likeness by similarity of environment. The point in which 
Professor Sachs’s plan seems to us open to criticism is his determination 
to bring together, under a common name, homoplastic organs of 
1 Origin of Species, ed. i., p. 434. 
