374 SECTIONAL TRANSACTIONS.—C. 
II. A critical re-examination of the recapitulation hypothesis in the light of recent 
ontogenetic studies, chiefly of fossil molluscs, shows that there are admittedly many 
features in almost every ontogeny which could not be paralleled with any stage in 
the phylogeny of the species. These features result from the introduction of new 
(ccenogenetic) characters, from the omission (‘skipping’) of stages which would 
unnecessarily prolong ontogeny, from the varied rates of acceleration of different 
characters (in some cases a group of characters is retained because of its suitability 
to the embryonic stages), and from other causes. Nevertheless, there appear to be 
certain features in the ontogeny of most fossil species which may reasonably be 
regarded as recapitulatorial. 
Prof. H. H. SwinnerTOon. 
As time is a vital factor in evolution the evidence of Paleontology is essential 
to the settlement of differences of opinion reflected in contending hypotheses. The 
fact that its material is made up mainly of fragmentary remains is more than balanced 
by the abundance of those remains ranging over vast periods of time. These fragments 
include the remains of both ancestral and descendant members of the same evolving 
stocks, and consequently the study of them confirms, corrects or amplifies conceptions 
based upon the study of embryology and comparative anatomy such as recapitulation, 
variation, species. Though paleontological evidence has, on the whole, kept closely 
in the wake of that furnished by other biological sciences, it has lagged behind in its 
contribution to those problems which are suggested by such experimental work as 
that associated with the term ‘ Mendelism.’ Whilst the experiments must be with 
carefully controlled living organisms belonging to immediately succeeding generations, 
the individual factors are permanent possessions of the whole racial stock, and new 
arrangements of them may be exhibited by many generations. A large proportion 
of the factors are preservable in the fossil state, and consequently their behaviour 
in different genetic stocks is capable of investigation. Factorial features exhibit 
the same independence of one another when traced along different lineages as they 
do when followed from parent to offspring through only a few generations. The 
evidence in that case confirms the findings of the experimenter. On the other hand, 
the study of fossils seems to indicate that some factors, when followed through 
geological time, undergo serial change. This runs counter to existing conceptions 
of the nature of the factor. Even with such limited attention as this aspect of 
paleontology has received there are indications that its evidence will prove to be just 
as valuable to this as to other branches of evolutionary inquiry. 
Monday, September 28. 
Discussion on Earth Movements in relation to Stratigraphy. (Prof. O. T. 
Jones, F.R.S.; Prof. E. B. Battey, F.R.S., and Dr. J. Weir; Prof. 
W. S. Boutron; Prof. H. A. Brouwer; Dr. G. L. Extzs; Dr. 
R. G. S. Hupson; Mr. D. L. Linton; Dr. E. O. Utricn; Prof. 
P. G. H. Boswe tt, F.R.S.) 
Prof. O. T. Jongs, F.R.S. 
A discussion on this topic must necessarily cover a wide range, as it is of interest 
not merely to geologists, but also to geophysicists and economic geologists, particularly 
oil geologists. I can do little more than call the attention of investigators in these 
various subjects to the different aspects of the problem. There are obviously two 
aspects to be considered, viz. the influence of earth movements on sedimentation and 
of sedimentation on earth movements. 
Both aspects bring us into contact with prevailing theories of the nature and 
behaviour of the deeper layers of the earth’s crust. In particular, there has to be 
considered the importance or otherwise of Isostasy in its relation to sedimentation 
on the one hand and earth movements on the other. 
It is obvious that earth movements exercise a dominant control over sedimentation, 
for whether the sediments be mainly clastic such as sands or muds, or non-clastic 
calcareous deposits, the thickness that can accumulate in any given period is limited _ 
