XXVIII INTRODUCTION. 
phosis, in accordance with which certain parts assume a 
different form from the rest, in order the better to fit 
them for the performance of different offices. Should 
erowth and development be uniform and regular, that 
is in accordance with what is habitual in any particular 
species, there is no monstrosity, but if either growth 
or development be in any way irregular, malformation 
results. Hence, theoretically, the best way of grouping 
cases of malformation would be according as they are 
the consequences of :—Ilst. Arrest of Growth; 2ndly. 
Excessive Growth; 38rdly. Arrest of Development ; 
Athly, of Excessive or Irregular Development. 
In practice, however, there are so many objections 
to this plan that it has not been found practicable to 
carry it out. The inability arises to a great extent 
from our ignorance of what should be attributed to 
arrest of growth, what to excess of development, and 
so on. Moreover, a student with a malformed plant 
before him must necessarily ascertain in what way it is 
malformed before he can understand how it became so, 
and for this purpose any scheme that will enable him 
readily to detect the kind of monstrosity he is examin- 
ing, even though it be confessedly artificial and im- 
perfect will be better than a more philosophical 
arrangement which circumstances prevent him from 
employing. 
The plan followed in this volume is a slight modi- 
fication of that adopted by Moquin-Tandon, and with 
several additions. In it the aim is to place before 
the student certain salient and easily recognisable 
points by reference to which the desired information 
can readily be found. Under each subdivision will be 
found general explanatory remarks, illustrative details, 
and usually a summary of the more important facts 
