I04 



ANDREWS. 



characteristic of contraction take place. There are always areas 

 or masses of substance which share passively in such displace- 

 ment, just as fluid alveolar inclusions do. In a Vorticella for 

 instance, displacement of the whole body mass is caused by . 

 contraction phenomena in certain cuticular structures, aided in 

 some cases by fibrils running through the body mass. Here 

 the statements should be taken as referring to the active areas, 

 not to the passive. Even in active areas there is much dis- 

 placement of passive material, but this is covered by the terms 

 of my statement. 



It is to be regretted that my researches do not throw more 

 light on the true nature of the initiative force in that mooted 

 property of the substance, — contractility. They seem, indeed, 

 rather to render final knowledge of this sort more difficult and 

 improbable than it was before they were made. Whereas be- 

 fore, the problem rested at a certain structure which could be 

 measured and dealt with optically to some extent, and if not 

 referable to this, could then be handed over to the physicists 

 for molecular hypotheses ; it has now receded, — still associ- 

 ated it is true with the same physical structure, — but far 

 beyond our optical resources. 



Yet perhaps we are not altogether losers by these new facts, 

 for, if, by withdrawing from our reach the elements of the 

 problem, they seem to tend to mystification, they bring also 

 new assurance that, so far down in the scale as substance and 

 substance changes of this sort can be traced, or even inferred, 

 we have still the same phenomena to deal with, and these are 

 still associated with the same physical facts of a certain struc- 

 tural organization of the two sets of protoplasmic elements. 

 By so much therefore they have more clearly defined the prob- 

 lem to be solved, the difficulties to be met ; making ready for 

 the touch of some master mind unified material without which 

 the truth might hardly be grasped. 



As far down as we go, we are still limited to seeing and 

 describing the effects of contraction rather than the actual 

 contraction phenomena. What we see is always displacement 

 of living substance by a wave-like impulse in the direction of 

 shortening, the displaced substance, then taking its way along 



