\ ■■•: :i brief introduction, Mr. Smith gave a general des- 

 cription, illustrated by drawings, of the eye of a spider, showing 

 how, in its simple structure, it differed widely from the compound 

 eyee of insects, but was strikingly analogous to the insect 



Qua Ilf then went on to discuss at some length the division, 

 l.v Mons. E. Simon, of spiders' eyes into two kinds — diurnal 

 and nocturnal ; and whilst agreeing with that eminent arach- 

 Doloerisi that the differences between the more advanced examples 

 of these two types were extremely distinct and of considerable 

 scientific importance, he considered that the so-called nocturnal 

 ey< a were rather of the nature of atrophied organs, impaired 

 by long disuse. The lecturer then went on to explain more 

 fully the structure of eyes of both types. Whilst it was certain 

 thai .in image of a very considerable degree of distinctness could 

 be produced by an eye-lens of the diurnal type, he believed 

 that the aborted and irregularly shaped "nocturnal" lenses 

 were quite incapable of producing anything like a clear image, a 

 1m -lief which was supported by the fact that in many cases the 

 retina seemed to have practically disappeared. Having treated 

 on the structure of the eyes, Mr. Smith went on to explain 

 the :irr;ingement of these organs in the more important of the 

 spider families, and to show how this arrangement and the 

 habits of the spiders were, as a rule, visibly interdependent. 

 In a few cases, however, curious exceptions had been discovered. 

 A species of Porrhomma, for example, had long ago been found 

 living in coal-pits, and as the eyes in this case were of quite a 

 rudimentary type, it had been surmised, at the time of 

 its discovery, that the underground darkness was the cause 

 of this optical imperfection. Mr. Smith stated, however, that 

 he had taken specimens of this very species amongst grass in 

 several parts of Middlesex and Essex, and these individuals 

 all ex hi hi ted eyes of the same rudimentary type as that 

 of the pit spiders. He suggested that in the struggle for 

 existence which must ensue between the vast numbers of 

 spiders introduced into coal-pits with the horses' fodder, the 

 species which was least dependent upon powers of vision would, 

 in the end, survive at the expense of those forms which were 

 embarrassed by the absence of daylight. Many species 

 of the families Linyphiidae and Theridiidae had, in the male, 

 curious prominences, usually supposed to enlarge the spider's 



