CHAPTER XIV. 
EMBRYOLOGY AND THE THEORY OF RECAPITULATION. 
BrEFoRE bringing into the discussion any evidence derived from the study 
of comparative embryology, it will be well to enquire briefly into the 
foundations upon which its arguments are based. Here as elsewhere the 
methods and opinions of the present time are founded on the knowledge 
and practice of the past: from time to time, it becomes necessary to re- 
examine the methods currently applied in any special branch of it, and to 
ascertain how far they are in accord with the general position of the science 
as a whole. It will be seen in the matter of embryology that as the point 
of view of the whole science has altered the methods and opinions of 
workers in this field have also undergone modification, and we must 
accordingly be prepared for still further changes so as to keep embryo- 
logical method in accord with the time. A short historical sketch will 
illustrate this, and at the same time it may give some better insight into 
the bases of embryological method as it exists at present. 
Embryology as a branch of the science of Botany can hardly be said 
to have existed before 1840. It is true that there was already some 
knowledge of the form and position of the germ in Flowering Plants. 
So early as the seventeenth century both Grew and Malpighi dissected and 
described the embryos of various seeds, while Ray, in his Astoria 
flantarum, founded the distinction of Dicotyledons and Monocotyledons on 
characters of the embryo. But up to the early decades of the nineteenth 
century the study of the early stages of development of the individual 
was not used as a systematic means of elucidation of the relations of 
plants. This method was introduced by Schleiden, who saw in the history 
of development the foundation of all insight into morphology. He founded 
the study of development of the flower, which has had such far-reaching 
effects on their comparison and systematic arrangement. He also gave 
special prominence to the initial embryology of the individual plant, and 
to comparison of the higher forms with the Cryptogams. Almost simul- 
taneously the details of cellular construction and of apical segmentation 
in the lower forms were revealed by Naegeli, and as he extended his 
