58 BARKER : 



there was no straight open path from one side of the table 

 to its opposite, or to any point which offered escape, but 

 a tortuous path could be found by an intelligent animal 

 endowed with distinct vision. Some of these cards were 

 white, some gray, and others dark brown or black ; otherwise 

 they were uniform. Under these circumstances the insects 

 placed upon the table seemed to be unable to distinguish 

 between solid bodies and open spaces until they either ran 

 against the former or examined them with their antennae, 

 while vertebrates under similar circumstances avoided the 

 obstacles without difficulty, as was anticipated. Of course, 

 the failures on the part of the insects may have been due to 

 ignorance or bad judgment. A confession of bad judgment 

 on the part of the investigator recorded against himself by 

 Plateau deserves mention. Winged insects of many species 

 were placed in a special dark chamber provided with two 

 windows, one of which was cross-barred or trellised, and the 

 other unobstructed, but of dimensions ensuring equal illumi- 

 nation. The details cannot be given here, but the observa- 

 tions recorded by Plateau seemed to justif}' his claim that 

 insects did not distinguish form, since they more frequently 

 attempted to pass through the trellis than through the other 

 window. Forel, however, was not convinced. He claimed 

 that the mistakes made by Plateau's insects were errors of 

 judgment which would occur with vertebrates under similar 

 circumstances. Thus challenged. Plateau tried the verte- 

 brates and frankly acknowledges that Forel was right, but 

 nevertheless believes that his experiments with the labyrinth 

 and other experiments in the open air were conclusive. 



On the anatomical side he had great faith in the work of 

 an American, W. Patten, whose most important discovery is 

 that a delicate plexus of nerve fibres occupies the upper part 

 of the crystalline cone, an expansion of a nerve bundle tra- 

 versing axially the entire length of the ommatidium, * except 



* A complete radial element or segment of the compound eye of an 

 arthropod. Plate I, Fig. 3. 



