Notes and Comments. 345 
species where reproduction is normal. The zoning between 
the brown seaweeds of a marsh is often very striking; but 
the factors governing it must be far more complicated than 
those operating on the seashore. The extensive mattings of 
brown seaweeds often found on English marshes have a de- 
cidedly beneficial effect on the phanerogams. — It seems possible 
that F. volubilis may act as a pioneer in the establishment of 
salt marshes in certain cases. 
MOMENTUM IN EVOLUTION. 
Professor Arthur Dendy stated that in 1909 ‘ Dr. Smith 
Woodward called the attention of the Geological Section to 
the fact that many groups of the animal kingdom in the course 
of their evolution have shewn a strongly marked tendency to 
enormous increase in size, often accompanied by the develop- 
ment of grotesque and apparently useless excrescences. Com- 
parative anatomists have long been familiar with analogous 
phenomena in such cases as the extraordinary development 
of the beak and helmet in the hornbills and of the tusks in the 
babirusa. In all the cases cited, and in many others which 
could be adduced, either the entire body or some particular 
organ appears to have acquired some sort of momentum, by 
virtue of which it has continued to grow far beyond the limit 
of utility, although perhaps in some cases a new use may be 
found which will assist the species in maintaining itself in 
the struggle for existence. An enormous increase in mere 
bodily size, however, seems in the long run to be always fatal 
to the race, whose place will be taken by smaller and more 
active forms. Is there any justification in recent developments 
of biological science for the belief that a race of animals may 
acquire a momentum of the kind referred to which may ul- 
timately lead it to destruction ? Is there some brake normally 
applied to the growth of organs and organisms, and if so, are 
there occasions on which the brake may be removed with 
tesults which ultimately prove fatal?’ The author then gave 
reasons for answering both these questions in the affirmative. 
MEAN SEA-LEVEL. 
Captain E. O. Henrici pointed out that in the report of the 
Royal Commission on Coast Erosion it is stated that there is 
some evidence that the land on the coasts of Northumberland 
and Durham is sinking relatively to the sea. The only method 
of determining whether this is so or not is by means of accurate 
observations of mean sea-level with reference to marks on 
shore. The sea-level is, however, constantly altering, not 
only with the tides, but also with the winds, height of barometer, 
and rainfall. Accordingly, in order-to determine what is 
mean sea-level it is necessary to take observations over a long 
period of years. Observations at some two dozen stations 
agtt, Oct. 1. 
