826 REPORT— 1890. 
Secrion D.—BIOLOGY. 
PRESIDENT OF THE SECTION—Professor A. MILNES MARSHALL, M.A., M.D., 
D.Sc., F.R.S. 
THURSDAY, SEPTEMBER 4. 
The PrusrpEent delivered the following Address :— 
As my theme for this morning’s address I have selected the Development of 
Animals. I have made this choice from no desire to extol one particular branch 
of biological study at the expense of others, nor through failure to appreciate or at 
least admire the work done and the results achieved in recent years by those 
who are attacking the great problems of life from other sides and with other 
weapons, 
My choice is determined by the necessity that is laid upon me, through the 
wide range of sciences whose encouragement and advancement are the peculiar 
privilege of this Section, to keep within reasonable limits the direction and scope 
of my remarks; and is confirmed by the thought that, in addressing those specially 
interested in and conversant with biological study, your President acts wisely in 
selecting as the subject-matter of his discourse some branch with which his own 
tudies and inclinations have brought him into close relation. 
Embryology, referred to by the greatest of naturalists as ‘one of the most im- 
portant subjects in the whole round of Natural History,’ is still in its youth, but 
has of late years thriven so mightily that fear has been expressed lest it should 
absorb unduly the attention of zoologists, or even check the progress of science by 
diverting interest from other and equally important branches. 
Nor is the reason of this phenomenal success hard to find. The actual study 
of the processes of development ; the gradual building up of the embryo, and then 
of the young animal, within the egg; the fashioning of its various parts and 
organs ; the devices for supplying it with food, and for ensuring that the respiratory 
and other interchanges are duly performed at all stages: all these are matters of 
absorbing interest. Add to these the extraordinary changes which may take 
place after leaving the ege, the conversion, for instance, of the aquatic gill- 
breathing tadpole—a true fish as regards all essential points of its anatomy—into 
a four-legged frog, devoid of tail, and breathing by lungs; or the history of the 
metamorphosis by which the sea-urchin is gradually built up within the body of 
its pelagic larva, or the butterfly derived from its grub. Add to these again the 
far wider interest aroused by comparing the life-histories of allied animals, or 
by tracing the mode of development of a complicated organ, eg. the eye or the 
brain, in the various animal groups, from its simplest commencement, through 
gradually increasing grades of efficiency, up to its most perfect form as seen in 
the highest animals. Consider this, and it becomes easy to understand the 
fascination which embryology exercises over those who study i. 
But all this is of trifling moment compared with the great generalisation which 
tells us that the development of animals has a far higher meaning ; that the several 
embryological stages and the order of their occurrence are no mere accidents, 
