President's Address. 315 



on. The Davy Medal is awarded to him in recognition of his great 

 merits and achievements as an investigator. 



DARWIN MEDAL. 

 Professor Giovanni Battista Grassi. 



The Darwin Medal for 1896 is awarded to Professor Grassi, of 

 Rome (late of Catania), for his researches on the constitution of the 

 colonies of the Termites, or White Ants, and for his discoveries in 

 regard to the normal development of the Congers, Muraense, and 

 Common Eels from Leptocephalus larvas. 



From a detailed examination of the nature and origin of the colo- 

 nies of the two species of Termites which occur in the neighbour- 

 hood of Catania, viz., Termes lucifugus and Callotermes flavicollis, he 

 was able to determine certain important facts which have a funda- 

 mental value in the explanation of the origin of these and similar 

 polymorphic colonies of insects, and are of first-rate significance in 

 the consideration of the question of the share which heredity plays in 

 the development of the remarkable instincts of " neuters," or arrested 

 males and females, in these colonies. Professor Grassi has, in facb, 

 shown that the food which is administered by the members of a 

 colony to the young larvae determines, at more than one stage of their 

 development, their transformation into kings or queens, or soldiers or 

 workers as the case may be, and the value of these researches is 

 increased by the observations which he has made on the instincts 

 of the different forms, showing that they do not in early life differ 

 from one another in this respect, and are all equally endowed with 

 the potentiality of the same instincts. These do not, however, all 

 become developed and cultivated in all alike, but become specialised, 

 as does the physical structure in the full-grown forms. 



A very different piece of work, but having a no less important 

 bearing on the theory of organic evolution, is that on the Lepto- 

 cephali. These strange, colourless, transparent, thin-bodied creatures, 

 with blood destitute of red corpuscles, had been regarded as a special 

 family of fishes, but have been proved by Grassi's patient and long- 

 continued labours to be larval forms of the various Mureenoids. The 

 most astonishing case is that of the Common Eel, Anguilla vulgaris, 

 the development of which had been a mystery since the days of 

 Aristotle. It had been long known that large eels pass from rivers 

 into the sea at certain seasons, and that diminutive young eels, called 

 in this country Elvers, ascend the rivers in enormous numbers. But, 

 although the species is very widely distributed, no one in any country 

 had been able to discover how the elvers were produced. Grassi has 

 shown that, large as the eels are that pass into the sea, they are not 

 perfectly developed fish, but only attain maturity in the depths of the 



