174 THEORY OF RECAPITULATION 
observations, which were thus initiated among the lower Cryptogams, to. 
the Archegoniatae and the Phanerogams, he secured that morphological 
ideas, hitherto drawn primarily from the Phanerogams, should be examined 
in the light afforded by the history of development in the Cryptogams. 
And thus the way was prepared for the brilliant embryological work of 
Hofmeister, who, after investigating the embryogeny of the Phanerogams, 
tracing the individual from the egg onwards, proceeded to apply the 
same method to the Bryophytes and Pteridophytes, with the results. 
which are now permanently interwoven into the web of the science. It 
may be said that subsequent work in this direction has done little more 
than to fill in the details in the areas of observation left blank upon the 
morphological map thus plotted in broad outline about the middle of the 
last century. It is in the interpretation of the facts, and the recognition 
of the evolutionary history which they convey that there has been room 
for some difference of opinion: and it is this that will now be discussed. 
While the elucidation of the facts by Naegeli, Hofmeister, and others. 
was proceeding, the belief in the mutability of species became prevalent :. 
the Darwinian theory seemed, as we have already seen, to provide a natural. 
explanatory thread running through the facts of genetic morphology and 
connecting them into an evolutionary history. It was held that the 
sticcessive events of the individual life directly illustrated the course of 
descent; as regards the sporophyte the first stages were accordingly 
regarded as phylogenetically the earliest, and consequently for comparative: 
purposes the most important. Embryological detail was thus given a high 
place in comparative morphology. Analogy with the results and arguments. 
of zoologists seemed to support this position, and just as some consistent 
reflection of the phylogenetic history was found in the beginnings of the 
individual life of the higher animals, so, it was held, should be the case- 
with the plant: the embryology of the sporophyte was accordingly made 
the basis of a consecutive history of its development in the race. For 
instance, the first formed leaves were held to represent the primitive and 
original foliar type, and those formed later on in the individual life were 
regarded as subsequent in the history of the race: or, carrying this line 
of thought further into detail, the order and position of the first segmenta- 
tions in the ovum were regarded as of special comparative importance, and 
were used as the basis of elaborate theorising. 
But before such conclusions are accepted, it is well to reflect upon 
the profound differences which exist between the embryology of the higher 
animals and that of the sporophyte in plants. In the first place, the 
embryogeny of the higher animal is carried out once for all after fertilisa- 
tion: the main parts are laid down at a comparatively early stage, and are 
not repeated later. But in the sporophyte of all Vascular Plants the 
initial embryogeny is merely a preliminary phase leading to that continued 
embryogeny which involves the repeated formation of parts: this is main-. 
tained throughout the active life of the plant. Hence the initial embryo- 
