SUMMAR y. 161 



attempt to follow the various lines. The general 

 history of the various groups is essentially alike. 

 The embryos are at first fundamentally similar, but 

 they soon become unlike, the time of separation de- 

 pending on the closeness of relation of the adults. 

 The more distant the relation of the adults, the 

 earlier the embryo separates. The general embryo- 

 logical history of all divisions is thus parallel to their 

 arrangement in a scheme of classification, a parallel 

 which is always subject to modifying circumstances, 

 as we have already seen. 



Vegetable Embryology. 



The embryology of plants is of little importance, 

 since it illustrates none of the significant principles 

 found in developing animals. The organization of 

 plants is so simple that an extended history would 

 be impossible, and seeds, moreover, are almost uni- 

 versally supplied with abundant food. Add to this 

 the fact that the embryology of plants and animals 

 has been studied in a very different manner and for 

 different purposes, and we discover the reason why 

 the vegetable kingdom gives us practically no evi- 

 dence from its developing embryos. 



Summary. 



We have seen that the study of adult anatomy 

 leads to an arrangement of the relations of groups 

 in the form of a branching tree. While it is evident 

 that this arrangement must be accepted, it is equally 

 plain that the study of adult anatomy alone will 

 never enable us to unite the various sub-kingdoms 



