182 Proceedings of the Royal Society of Edinburgh. [Sess. 
Yves Delage. By Professor J. H. Ashworth, F.R.S. 
(Read January 9, 1922.) 
The loss of Professor Yves Delage is deeply felt by a wide circle of friends 
and fellow-workers by whom he was held in the highest esteem for his 
outstanding merits as an investigator and for his unaffected simplicity. 
He was a pupil of Lacaze-Duthiers, and obtained his doctorate in 1881 for 
his “ Contribution a l’etude de l’appareil circulatoire des crustaces edrioph- 
thalmes marins.” His next important work was his famous memoir (1884) 
on Sacculina, in which he described the structure and made known for the 
first time the complete life-history of this remarkable parasitic crustacean 
and its extraordinary relations to its host (crabs). Succeeding memoirs 
dealt with Balaenoptera, the histology of Convoluta, the functions of the 
semicircular canals — Delage was not only a first-rate morphologist, but a 
keen physiologist, — with the otocysts of invertebrates as organs of orienta- 
tion, and with the development of siliceous and fibrous sponges. 
In. 1895 appeared his stimulating book on Lheredite et les grands 
yproblemes de Biologic generate , an impressive example of the great extent 
of his knowledge and the clearness of his outlook. In this volume, Delage 
discussed in masterly fashion the structure of protoplasm, development, 
heredity, the evolution of species, and the principal theories relative to 
these subjects. In his views on evolution he was definitely Lamarckian, 
and on many points opposed to Weismannism. By this time he had turned 
his attention to the factors — external and internal — which determine the 
development of the egg, and he propounded a theory to account for the 
activation of the egg which led him to the experiments on artificial 
parthenogenesis with which his name (and that of Jacques Loeb) will ever 
be associated. He was able, by treating eggs of sea-urchins in hypertonic 
sea water alternately with tannin and ammonia, to activate them, and he 
succeeded in rearing some of the resulting larvae through their meta- 
morphosis. His researches in this domain extended over some ten years. 
His last published work (1920) is an important volume on dreams, in which 
he discussed the principal theories, psychological and physiological. A 
list of his publications shows not only his wonderful output of first-rate 
work — for his industry was extraordinary — but also his many-sided 
intellect. 
Delage rendered notable service to biology by founding in 1895 
