116 
obtain an affinity-group by the direct observation of natural affinity, as 
ENGLER says in §2. Such groups, according to his statement”, exist 
only in species, genera, families or in series. In other words, natural affinity 
is to be found between one individual and another individual belonging to 
the same species, between species and species belonging to the same genus, 
between genus and genus belonging to the same family, between family and 
family belonging to the same series; but there is generally no phylogenetic 
relation between series and series. Consequently, in his system, species, 
genera, families are, as far as his statement is concerned, arranged according 
to their natural affinity; while the series are not so arranged. Jt follows, 
therefore, that the series are arranged, according to their degree of advance- 
ment, or according to their simplicity or complexity, or according as they are 
primitive or reduced. His system is locally, in this part or that, natural in 
the sense that it denotes a certain relation of blood - kinship or a constitutional 
resemblance ; but his system, taken as a whole, is an artificial system, the 
series of which are arranged according to their degree of advancement, or to 
some such idea. As for the recapitulation theory which is given by him in 
§ 2, as a means of determining natural affinity, it is in many cases especially 
in plants not to be relied upon”. The other experimental method given by 
him is something that can be seen only in some few special cases. He says 
that it is necessary to ascertain affinity through the study of the development 
history. I think that is truly indispensable for finding the mutual velations 
in the case of development; but I think it is equally necessary that we should 
take into account the resemblance in the adult stage; the natural relation of 
young forms is sometimes different from that of adult forms, so that the real 
natural relation is only conceivable in its dynamic phase. He writes as 
follows” especially for the higher plants :— 
Dagegen sind wir bei der Feststellung der Verwandtschaft hdherer sipuen 
gendtigt, auf indirektem Wege die nattizliche Verwandtschaft zu ermitteln, und 
dabei leicht irrtiimlichen Auffassungen ausgesetzt. 
1) Enctmr, A. — Erlauterungen, 1. v. p. 362. 
2) Scuours, J. C.— Die Stelur-Theorie, p. 138 (P. Noordhoff Groningen, 1902). 
3) Encien, A.—l.c. p. IX. 
