660 : CONCLUSION 
evolution of the sporophyte was essentially different from that so constantly 
seen in their individual development. Here it is held that unless good 
reason be found to the contrary, the development of the individual will 
probably reflect in some degree the evolution of the race; but it is 
recognised that the principle is not directly applicable in all cases (Chapter. 
XIV.).1 Accordingly the ontogenetic facts would support a view involving) 
the appearance of new structures in the course of descent. 
We have seen that the first steps in the organisation of a sporophyte 
are suggested by the post-sexual divisions in certain Algae which there is 
good reason to believe were associated with a reduction of chromosomes. 
Passing from these initial stages of the sporophyte, of which the post- 
sexual stage in certain Algae cannot be held as more than suggestive of 
what actually occurred, to those where it appears as a more or less 
extensive tract of tissue, it has been shown that the sporogonia of Bryo- 
phytes provide numerous examples of sterilisation, and that the result has 
been to defer the event of reduction, and in various ways to increase the 
means of nutrition and dispersal of the spores (see pp. 258-286). The 
facts of sterilisation and their biological results have been accepted by 
other writers, and though they do not actually demonstrate that the 
sporogonium of the Bryophyte did originate by intercalation of a new 
phase in the life-cycle, nevertheless the observed facts harmonise with that 
view: it is difficult, without having recourse, as some have done, to purely 
hypothetical preliminary phases in the descent of this phylum, to read the. 
facts in any other way. . 
One important point on which the Bryophyta differ markedly in their 
individual development from all Vascular Plants, is that in them, as a rule, 
the whole sporophyte originates by a primary embryogeny: it is initiated 
directly from the zygote with the minimum of apical or intercalary growth, 
and with entire absence of appendages.?_ There is no continued embryogeny, 
with secondary initiation of fresh parts, as in Vascular Plants. This simple 
1There are two leading features of development to which a theory of recapitulation 
will not apply, and both are open to a biological explanation. The one is where those 
gouty developments occur in the embryogeny, especially in the Lycopods (p. 351), the 
other is the apparent priority of the vegetative system over the spore-production in the 
individual life. In both cases the recapitulation of the sequence of developmental events ; 
may be held to have been overruled by physiological requirement: the latter is fully 
explained on the basis first of sterilisation of individual cells, and secondly of abortion 
of the spore-producing parts: the consequence is that the vegetative system appears before 
the spore-production begins; though the latter was the prior function of the sporophyte, 
the overruling requirement was for early nutrition. The former has its origin in the 
demands of early nursing of the embryo, and it has been shown that it has arisen 
along two distinct lines within the genus Lycopodium. Such responses to biological 
requirement are readily intelligible ; but they must not be held to invalidate the whole 
doctrine of recapitulation, they show rather that it applies within limits only, and that 
the evolutionary story which the individual may tell is liable to secondary ‘disturbance. 
2 An exception is seen in Zrzopus, in which rhizoids appear at the base of the seta; 
this appears to be a good example of the origination of new organs not fashioned out 
of pre-existing organs (Goebel, Flora, 1906, pp. 66, 68). 
