PRESIDENTIAL ADDRESS. 207 



that one of His ^Majesty's Judges should speak of the formation of a great 

 collection of butterflies — a most valuable asset for bionomic research — as the 

 ' gratification of an infantile taste.' This or that collector may be an unscientific 

 person, but it would be easy to show that the study of insects in general, and 

 of butterflies in particular, is one of the most eflficient of the instruments in our 

 hands for arriving at a soiutiou of fundamental problems in biology. 



My second and final point is this. I have not hesitated to attirm my con- 

 viction of the importance in evolution of the Darwinian doctrine of natural 

 selection. This necessarily carries with it a belief in the existence and general 

 prevalence of adaptation. I am willing to admit that at times too much 

 exuberance may have been shown in the pursuit of what Aubrey Moore called 

 ' the new teleology.' ' Men of science,' it has been said, ' like young colts in a 

 fresh pasture, are apt to be exhilarated on being turned into a new field of 

 inquiry ; to go off at a hand-gallop, in total disregard of hedges and ditches, 

 to lose sight of the real limitation of their inquiries, and to forget the extreme 

 imperfection of what is really known.' This is not the utterance of some cold 

 outside critic, but of a great exponent of scientific method — no other than Huxley 

 himself. It may be true of some of the wilder speculations of Huxley's date. 

 I am by no means sure that there is not trutli in it as applied to some of the 

 developments of a later time. But however wide of the mark our suggested 

 explanations and hypotheses may be, the net result of all our inquiries, after 

 the gradual pruning away of excrescences and superfluities, will be a real 

 advance into the realms of the unknown. We may feel perfectly assured thai 

 the objections so far brought against our own interpretations are null and void, 

 but we may yet have to give way in the light of further knowledge. ' Let us 

 not smile too soon at the pranks of Puck among the critics ; it is more prudent 

 to move apart and feel gently whether that sleek nose with fair large ears, may 

 not have been slipped upon our own shoulders. '^ 



The following Papers were then read : — 



1. Some Further Experiments in the Artificial Production of a Double 

 Hydrocoele in the Larvce of Echinus miliaris. Bij Professor E. W. 

 MacBeide, F.R.S. 



In January 1918 I read a paper before the Royal Society in which I described 

 a method of producing a second hydrocoele [i.e., a rudiment of the water- 

 vascular system) in the larvae of the common shore-urchin, Echinus miliaris. 

 During the last year I have repeated my experiments and obtained a complete 

 confirmation of my previous results, with the addition of some further inter- 

 esting details of which I propose to give now a short account. 



The method which I outlined in my paper of 1.918 was as follows : — The 

 ripe urchins were obtained from Plymouth, and they were opened immediately 

 on their arrival in London, and the eggs shaken out into clean sea- water which 

 had been purified by being shaken up with charcoal and subsequently passed 

 through a Berkfeld filter. After development had gone on for three days 

 and the eggs had become transformed into four-armed plutei, these larvfe were 

 traneferred to water the salinity of which had been eiihanced by the addition 

 to it of 2 grams of NaCl per litre. In this hypertonic water they remained 

 for seven days, and they were then retransferred to ordinary sea-water. At 

 the age of about twenty-one days the extra hydrocoele which was situated on 

 the right side of the larva began to develop. The experiment was only carried 

 on till the larvae were a month old, by which time metamorphosis had not 

 been accomplished. The largest proportion of larvte with two hydrocoeles 

 which was obtained in any culture was 5 per cent. 



These experiments, which were carried out during the summer of 1917, were 

 the culmination of a series which were begun in 1914 and carried on during 

 the summers of 1915 and 1916. The reason that the larvsc, after being exposed 

 to the hypertonic water for a week, were retransferred to normal sea-water 

 was that I experienced great difficulty in getting the diatom Nitzschia, which 



* Dowden. 



