408 UR. J. C. MOXTRAM ON 



patterned backgrounds. There remains to be examined only 

 the fourth condition, in which the object cannot be seen though 

 both the object's and the background's patterns remain visible.. 

 This invisibility is due to a great similarity between the patterns 

 of object and background in size, shape, and relative tone of the 

 components. It is obvious that the most conspicuous pattern 

 will be inconspicuous against a background made of a similar,, 

 or closely similar, pattern. For this reason, under these special 

 conditions, it is not possible to define a pattern which will be 

 especially conspicuous, unless the pattern of the backgi'ound is 

 also defined. 



It may be concluded, therefore, that the pattern which has 

 been called the, white centre eye-spot pattern is a most con- 

 spicuous one against .eveiy backgroimd with the exception of 

 backgrounds themselves composed of eye-spot patterns. It follows, 

 that in Nature the white eye-spot pattern must be very con- 

 spicuous, provided that this type of pattern is not continuously 

 found as a background. 



White centre eye-spot patterns in Natxire. — Natural backgrounds, 

 were examined in ordei' to discover whether this type of pattern 

 was to be found and to what extent, and it was at once noticed 

 that they were very uncommon ; a morning's foray amongst 

 woods, fields, hedgerows, and broken country resulted in only 

 a fcAv examples. It is not difficult to make such patterns- 

 artificially out of doors ; for instance, by laying round white 

 stones on circular patches of dark moss, by placing shining leaves, 

 over dark rough ones, by viewing pierced leaves against the light, 

 and in many other ways. Natui'al eye-spot patterns may be 

 conveniently described under the following headings : — 



1. On hare ground. — (a) Due to irregularities of the surface. 

 Working with plasticene the pattern can be produced by a 

 shallow conical pit with a flat bottom, by a truncated cone lying- 

 on its base, or by a cylinder standing in the middle of a cylindrical 

 depression ; in each case top lighting is necessary. Viewed from 

 above, a light centre dark-maigin ciiTular pattern is seen ; the 

 pattern does not perfectly reproduce the one desired, because 

 the centre instead of being lighter in tone than the background 

 is either of the same tone or somewhat darker. It is evident 

 that by artificial methods this pattern can only be reproduced 

 with difticulty, and thus its occuiTence in Nature must be very 

 i-are. By prolonged search isolated examples are to be seen. 



(h) Due to the surface being of broken tones ; a light stone 

 or one reflecting the light from the sky when lying on a circular 

 dark patch will give rise to the pattern. Examples of this 

 nature are not difficult to find, but they are never numerous 

 and always isolated. 



2. On grass and other short vegetation. — Except for flowers, 

 which are considered elsewhere, the eye-spot pattern is very 

 rarely seen ; occasionally light reflected from a shiny leaf supplies 

 an example. 



