110 SECTIONAL ADDRESSES. 
Among the notable features of zoological activity during the last 
twenty-five years the amount of work on the physiology of organisms 
other than mammals must attract early notice in any general survey of 
the period. Eighty years ago Johannes Miiler’s physiological work 
was largely from the comparative standpoint, but for some years after 
his death the comparative method fell into disuse, and the science of 
physiology was concerned chiefly with the mode of action of the organs 
of man or of animals closely related to man, the results of which have 
been of outstanding importance from their bearing on medicine. Interest 
in the more general applications of physiology was revived by Claude 
Bernard (‘ Legons sur les phénoménes de la vie,’ 1878), and the appear- 
ance of Max Verworn’s ‘ General Physiology,’ in 1894, was in no incon- 
siderable measure responsible for the rapid extension of physiological 
methods of enquiry to the lower organisms—a development which has 
led to advances of fundamental importance. Many marine and fresh- 
water organisms lend themselves more readily than the higher verte- 
brates to experimentation on the effects of alterations in the surround- 
ing medium, on changes in metabolic activity, on the problems of 
fertilisation and early development, on the chemistry of growth and 
decline, and to the direct observation of the functioning of the individual 
organs and of the effects thereon of different kinds of stimuli. The 
study of these phenomena has greatly modified our interpretation of 
the responses of animals and has given a new impetus to the investiga- 
tion of the biology and habits of animals, i.e. animal behaviour. This 
line of work—represented in the past by notable contributions such as 
those by Darwin on earthworms, and by Lubbock on ants, bees and 
wasps—has assumed during the last two or three decades a more 
intensive form, and has afforded a more adequate idea of the living 
organism as a working entity, and revealed the delicacy of balance 
which exists between structure, activity and environment. This closer 
correlation of form, function and reaction is of the greatest value to 
the teacher of zoology, enabling him to emphasise in his teaching that 
for the adequate appreciation of animal structure a clear insight into 
the activities of the organism as a living thing is essential. 
The penetrating light of modern investigation is being directed into 
the organism from its earliest stage. During the summer of 1897 
Morgan discovered that the eggs of sea-urchins when placed in a two 
per cent. solution of sodium chloride in sea-water and then transferred 
to ordinary sea-water would undergo cleavage and give rise to larvx, 
and J. Loeb’s investigations in this field are familiar to all students of 
zoology. Artificial parthenogenesis is not restricted to the eggs of 
invertebrates, for Loeb and others have shown that the eggs of frogs 
may be made to develop by pricking them with a needle, and from such 
eggs frogs have been reared until they were fourteen months old. The 
application of the methods of microdissection to the eggs of sea-urchins 
is leading to a fuller knowledge of the constitution of the egg, of the 
method of penetration of the sperm, and of the nuclear and cytoplasmic 
phenomena accompanying maturation and fertilisation, and will no 
doubt be pursued with the object of arriving at a still closer analysis of 
the details of fertilisation. 
