CHAS. \V. HAR(iITT. 



The two suspended specimens continue as before, one absolutely 

 as at first, the other with a definite crescentic curvature, but 

 forty-five degrees away from light. Fig. 4 is from a photograph 

 taken ly Dr. S. \\. Williams and gives a good impression of the 

 orientation of such specimens as came within the view. It is 

 taken from the end in order to show the relation of the tubes 

 to light, which came directly from the right and into that side 

 of the aquarium. Of the twenty specimens only eight are shown, 

 and of these only one faces the light, one is almost vertical, the 

 other six incline very definitely toward the dark side of the 

 aquarium. 



As will be seen, nothing especially new has developed beyond 

 what has been found in connection with the earlier series. How- 

 ever, since here the conditions of light, temperature, etc., have 

 been so ideal the results not only confirm those already given, 

 but render them more certain and conclusive. It seems quite 

 improbable that three series of experiments directed to a single 

 end should have given uniformly erroneous results; moreover, 

 it is equally improbable that any error of method should have 

 vitiated all three series, varied as these are shown to be, and 

 inspected as they were by several of my colleagues almost from 

 the beginning. Nor is it possible that the matter of season could 

 have been a modifying factor, for it coincided almost exactly 

 with that of Loeb's experiments. That light has been shown to 

 be a wholly negligible factor in relation to the behavior in (JIM -lion 

 has not at any time been claimed. That it has been shown to 

 have only a minor influence I believe the facts conspire to render 

 very certain. 



But we are not yet done with the problem. In his original 

 account Loeb cited the behavior of Spirographis in the public 

 aquarium as tending to confirm his experimental results "for the 

 most part' I have studied the problem in this aquarium with 

 especial care during the entire course of my own experiments 

 and have found the behavior to confirm my experiments, as the 

 results will show. Let it be expressly understood that in these 

 large exhibition aquaria the best efforts of many years have been 

 directed to render them as nearly natural as it is possible to 

 have such limited portions of the sea; and the fact that some 



