208 [December 



of diflferent patterns. If, then, these two species did not spring from 

 some pre-existing form, but were created originally as distinct species, 

 how does it come about that the same very peculiar pattern is repeated 

 on the thorax of each ? What possible necessity in that case could 

 there be, for Nature to plagiarize from herself a merely ornamental de- 

 sign, when millions and millions of other designs might just as well, for 

 anything we can see to the contrary, have been selected ? I could as 

 soon believe, with the old geologists, that dead fossil shells had been 

 created in the rocks, on purpose to deceive us into believing that they 

 had once been alive, as that, out of the infinity of possible patterns, a 

 particular one had here been selected and imprinted upon two aborigi- 

 nally distinct species, with the manifest result of deceiving us into con- 

 founding those two species together. 



I have said that there are tt/picaUy eighteen spots on the thorax of 

 the above two species. Sometimes, however, six particular spots out of 

 the eighteen are some or all of them absent, the locus of the remaining 

 spots being still the same ; and it is very remarkable, that in the two 

 species it is the same particular spots that are thus absent, viz: the two 

 minute ones on the dorsal line and the central one of each quincunx, 

 which are often absent, and the spot in each quincunx that abuts on the 

 hind angle of the thorax, which is but seldom absent. According to the 

 mathematical theory of chances, this can scarcely be a merely fortui- 

 tous event; for the odds are enormously against any one's happening 

 on the same pai'ticular six numbers, twice over, out of eighteen numbers. 



It is sometimes the case also, in both the above two species, that se- 

 veral pairs of the thoracic spots are confluent with each other. Now 

 we have only to imagine all of them confluent, and we get the thoracic 

 ornamentation found in Chrijsomcla biijshi/ana Kby, C.prsecehis Rogers, 

 C. elegans Oliv. and C. exdamationis Fabr., viz: a dark-colored thorax 

 bordered latei'ally and in front with a pale tint; and in C scripta Fabr., 

 C. interrupta Fabr., C. Adonklia Fabr., and especially in C. midtipuiic- 

 tata Say, we find intermediate grades between the two forms. Nor is 

 this an entirely imaginary idea as applied to the genus Chrij&oincla. 

 In a series of specimens of one species of this genus, Interrupta Fabr., 

 as I have already observed, {Froc &,c. III. pp. 228-9,) we find, as re- 

 gards the elytral markings, precisely the same gradations, from sixteen 

 dark spots more or less partially confluent, to a uniform dark color bor- 

 dered laterally and behir.d by a pale tint. Nobody doubts that these 

 colorational varieties of the species interrupta have all proceeded from 

 a common origin. Why then should we be shocked with the idea, that 



