PERIODICITY IN ORGANIC LIFE. 51
There is no very remarkable feature to record ; but the general
condition of the bones gives evidence of a non-adult animal,
especially the epiphyses of the dorsal and lumbar vertebras, which
are distinct, though loosely adherent to the body of each vertebra.
In the cervical vertebra they are nearly free, and in the caudal they
are mostly loose plates. Mr. Gerrard informs me that the vestigial
remains of the hind limbs were only two small pieces of cartilage.
The sternum of this species differs very greatly in individuals,
and varies also in shape, according to the age of the animal. The
median notch in the presternum forms, in the Burnham specimen, a
relatively large pear-shaped sinus.
It may be interesting to append a few of the measurements I was
enabled to make :—
P.S.—Since the above was written, I have been informed by Mr.
A. Newman that he has sold the skeleton, and it is now in a museum
at Grimsby.
PERIODICITY IN ORGANIC LIFE.
By HENRY LAVER, M.R.C.S., F.L.S., F.S.A.
Being the Presidential Address, delivered at Chelmsford, April 15th, 1893.]
I HAVE used this term "Periodicity" to indicate that state or
condition of a species, either animal or vegetable, which most
of those who have paid much attention to natural history in any of
its branches must have noticed. I mean that there are periods, not