339 



range of vision by elevating the eyes. The lecturer greatly 

 doubted the accuracy of this, giving several reasons for his 

 conclusions, amongst them being the fact that the elevations 

 were in many cases quite independent of the eyes — in some 

 instances even apparently interfering with their natural 

 functions ; and also that when the eyes were greatly elevated, 

 they were often quite atrophied. The genus Savignia, for 

 example, was formulated by Black wall for a species which 

 he believed to have only six eyes, quite overlooking an atrophied 

 pair which were placed at the summit of the slender caput. 

 The lecturer, who had illustrated his remarks by a number 

 of clever sketches, concluded by alluding to the experiments 

 which were necessary in order to test the powers of vision in 

 spiders. Very little work had been done in this direction, and 

 he ventured to recommend the subject to those members who 

 required a new line of research. 



Dr. Karop said that he must congratulate Mr. Smith upon 

 his admirable lecture. While admitting the strong resemblance 

 to eyes which many of these organs possessed, he preferred to 

 maintain an open mind on the subject, and he had great doubt 

 as to whether some of them, at any rate, were not organs 

 endowed with senses beyond our knowledge, and not eyes at 

 all in an optical sense. It had been proved long ago by 

 Spallanzani, and the experiments had been verified since his 

 time, that such a highly organised vertebrate as the common 

 bat was not dependent on sight for its sense of direction. Bats 

 which Spallanzani had deprived of sight were found to fiV at 

 full speed, and without hesitation, through apertures no larger 

 than their own bodies ; and when such a bat was released in 

 a room crossed by a network of fine threads, the animal flew 

 about without touching these threads. He then caught the 

 bat and sealed its external ears with wax, and found, on again 

 releasing it, that it could no longer find its way between the 

 threads without striking them. This proved that the animal 

 saw things not only by optical vision, but also by wave vibrations 

 transmitted through the external ear ; and if this were the 

 case in a highly organised vertebrate, there surely could be 

 no need to insist upon the possession of true optical vision in 

 insects and spiders. 



After considerable discussion, in which Messrs. Wesche, 

 Journ. Q. M. C, Series II.— No. 58. 24 



