38 
THE SHAPES AND SIZES OF ANIMALS. 
By Prof. A. MILNES MARSHALL, M.A., M.D., F.B.S., de. 
October 11th, 1892. 
The President (Mr. W. A. Waddington), in a few inaugural 
remarks, referred to the historic address given by Dr. Coultate, 
and remarked that there were four former Presidents of the Club 
still actively associated with the Club. He paid a graceful 
tribute to the memory of the late Dr. Anningson, one of the first 
members, and whose kindly presence and consistent interest 
cannot soon be forgotten. Societies like ours, the President 
said, are frequently not long lived, but he expressed the opinion 
that if the Club’s work were level with its standard, there is 
enough culture in the town to keep it up for any number of 
years. The Club was constituted of men of many moulds, and 
he hoped it would long be a quiet haven for studious minds. 
The lecturer pointed out that it is not a mere matter of chance 
that animals have certain characteristic shapes; these are 
correlative with their habits as well as subject to other laws. So 
too with the size of animals; for each animal there is a certain 
standard of size which is rarely very greatly departed from. 
Among the simplest animals, or Protozoa, it is characteristic 
of the more primitive genera, that there should be no definite or 
consistent shape ; it is possible, however, to speak of a distinct 
shape when these lowly forms are at perfect rest. This spherical 
shape is very characteristic either of the normal condition or of 
the resting state of a large number of Protozoa, and there is 
reason for thinking that this shape is not merely the simplest 
which an animal can offer, but is also the most primitive. 
The next characteristic shape met with in animals is that 
known as radially symmetrical, an ordinary jelly-fish being an 
excellent example of this shape which is found in the group of 
Coelenterates : here there is an antericr and posterior end, but 
no distinction between dorsal and ventral surfaces, or between 
right and left sides. Radial symmetry is confined to aquatic 
forms, the reason for this is the same as in the case of the still 
more primitive spherical form, 7.¢., that it is only in the case of 
animals, whether young or adult, which live immersed in fluid, 
that the relations between the animal and the surrounding 
medium are such as to allow of the animal having identical 
relations to the environment, whichever part of its circumference 
happens to be uppermost or undermost. 
