The results of these experiments led him to infer the existence of a very fine plexus of nerve fibres, in which the constituent threads cross and re-cross one another without actually coalescing. This conclusion, which he arrived at from purely experimental grounds, was some years afterwards confirmed by minute histological research. Finally, the effect of various poisons, chloroform, alcohol, &c., was tried, and the striking resemblance of their action on the nervous system of the Medusæ with that which they exert on that of higher animals supports the belief that nerve tissue when it first appears in the scene of life has the same fundamental properties as it has in higher animals. This piece of work was important, as the facts threw light, as Professor Sanderson has said, on elementary questions of physiology relating to excitability and conduction, and it was a characteristic of Mr. Romanes that in all his work, of whatever kind, he was always searching for principles. The minutest detail never escaped his attention if it appeared at all likely in any way to throw light on some biological or psychological problem. Only a trained scientific worker can appreciate the amount of labour these Royal Society papers represented. In 1875 he gave a Friday evening lecture at the Royal Institution on his work on Medusæ. He was also at this time working on the subject of 'Pangenesis,'[7] and a series of letters to Mr. Darwin and to Professor Schäfer may interest some readers. 18 Cornwall Terrace, Regent's Park, N.W.: January 14, 1875. Dear Mr. Darwin,--I should very much like to see the papers to which you allude. _A priori_ one would have thought the bisecting plan the more hopeful, but if the other has yielded positive results, in the case of an eye and tubers, I think it would be worth while to try the effect of transplanting various kinds of pips into the pulps of kindred varieties of fruit; for the homological relations in this case would be pretty much the same as in the other, with the exception of the bud being an impregnated one. If positive results ensued, however, this last-mentioned fact would be all the better for 'Pangenesis.'