tity and so entirely on the suddenness of the illumination, that a 

 series of instantaneous exposures at intervals of two seconds produces 

 in a given time a greater effect than continuous illumination from the 

 same source for the whole period a proof that in this case the action 

 in question is "liberated," not "maintained," by light. The re- 

 markable capacity for experimental investigation which was exhibited 

 in these and in his earlier physiological studies made it a matter of 

 regret to many of his friends that he did not continue them. 



An account must now be given of his work in the field of general 

 biology. His interest in Darwinian questions dates from the time 

 which preceded and followed his becoming acquainted with Mr. 

 Darwin in 1874. This acquaintance soon ripened into a friendship, 

 to the reality of which the writer can testify. It was promoted first 

 by the fact that in those early student days, Romanes' mind was, so 

 to speak, steeped in Darwinian doctrine ; but it owed its permanence 

 to his possessing certain rare and brilliant intellectual qualities which 

 Mr. Darwin highly appreciated. 



As he himself tells us (see ' Nature,' vol. 8, p. 432, 1873), it was in 

 discussing with Mr. Darwin some of the cases in which the effects of 

 disuse appear to be inherited, that his attention was directed to a 

 principle now held by many biologists to be of great importance 

 that of the action of " panmixia " or "negative selection" (Weis- 

 mann), or as Romanes at that time called it, " cessation of selection." 

 His claim to priority in this matter was, however, weakened by the 

 circumstance that he did not set forth this principle as of universal 

 application as the only way by which, consistently with the recogni- 

 tion of the " all sufficiency of natural selection " (Weismann. * Cont. 

 Review,' p. 334). the disappearance of superfluous organs can be 

 accounted for. Another subject of interest to him was also of 

 directly Darwinian origin. It seems to have been suggested by a 

 well-known passage in which Mr. Darwin pointed out that specific 

 characters which " do not affect the welfare of the species " cannot 

 be attributed to natural selection (' Origin,' 6th ed., p. 176). Romanes' 

 ideas on this point did not take form until, in 1886, he communicated 

 to the Linnean Society his well-known article on " Physiological 

 Selection ; an additional Suggestion on the Origin of Species." The 

 title was perhaps an unfortunate one, for it suggested a purpose which 

 was very far from being that of the writer. It seemed like an attack 

 on the fundamental doctrine of the ' Origin.' Notwithstanding its rather 

 speculative character, the essay on " Physiological Selection " must 

 be considered as the most important of his biological writings, for 

 it sets before the reader, in terms which cannot be mistaken, that 

 if by species is meant an association of animals or plants which is 

 distinguished by the incapacity of its members to unite sexually with 

 outsiders, the coming into existence of this disability as a barrier 



