14 peoceedin^gs of the 



Pkesidential Address. 



I]sr the Museum under my cliarge there is a small section which is 

 devoted to the illustration of the various organs and structures 

 which are concerned in locomotion. It has long been my desire 

 to render this group more complete, and not to be satisfied with 

 merely showing the organs by which this important function is 

 accomplished, but to show also, so far as is possible, the precise 

 way in which it is effected, making preparations which shall 

 illustrate the various phases of locomotion, the movements of the 

 limbs, and the carriage of the body in the act of locomotion. It 

 is impossible, of course, to do that which would be the best of 

 all, namely, to keep the animals alive in order to exhibit their 

 paces ; but the next best thing would be, in my opinion, to have 

 them preserved in such positions as would show their various 

 natural attitudes in these important acts of their lives ; and to 

 that end I recently paid a short visit to Plymouth, where I was 

 able to watch the movements of sundry animals in the Station of 

 the Marine Biological Association. 



The remarks which I have now to offer are mainly the result 

 of these observations, together with a few other collateral matters 

 which are closely allied to them. I may state, however, at once 

 that I do not pretend to much originality in these results. 

 Much of what I noted has been most likely observed by others 

 and described by them ; but in a few cases at least I think there 

 may be some degree of novelty. 



In the first place, as regards the method which I adopted in 

 making my investigations, a few words seem desirable, for many 

 persons, probably, may have opportunities of extending these 

 observations, and it is as well, perhaps, to proceed on lines which 

 have been found to be more or less successful. To attemj)t to 

 follow with one's eye the twinkling action of the feet (if I may 

 so use the term) — the rapid movements of the limbs — is a bafSing 

 and difficult proceeding; but I found that by very carefully 

 fixing the attention solely upon one pair of limbs at a time, it was 

 possible, in the majority of cases, to see what the rhythm was : 

 watching, for instance, in the first place, the first pair of limbs, and 

 seeing whether those of the opposite side were in opposite phases 

 of movement. That being determined, one could then carefully 

 observe and compare the movements of contiguous limbs on the 

 same side, looking only at two, and disregarding all the others. 

 By carrying on this process, one could soon arrive at the actual 

 rhythm of limb movement, and the position of various parts, in 

 the majority of cases. Clearly, however, where the movement 

 was still more rapid, the eye could not follow it, and then instan- 

 taneous or very rapid photography was needed. I found it 

 necessary to use a shutter giving an exposure of the 150th of a 

 second. 



One of the first forms which engaged my attention, because 

 one of the commonest on our coast, is a crab whose movement is 



