160 THOUGHTS ON SPECIES. 



structure, ornamentation or biography of the embryo,— any 

 differences in pupation, or any essential or specific variation 

 in the structure of the perfect insect ? By no means. To 

 be a variety, or wandering from a certain specific type, it 

 must observe the same biographical and organic cycle, pos- 

 sess the same specific characteristics of structure in its perfect 

 state, but differ from the species in its peculiarities of orna- 

 mentation, and in its size, perhaps to a degree that, without a 

 knowledge of its embryology and biography, it would be 

 pronounced and registered distinct from the perfect indivi- 

 duals towards which it shows the strongest specific affinities 

 of structure. Another characteristic of the variety is, that 

 there is no stability even in the peculiarities of its ornamen- 

 tation ; and whether it occurs in the same brood under iden- 

 tical climatal conditions, or is found as an isolated perfect 

 being in a widely-separated geographical area under dissi- 

 milar conditions, it must be associated with its normal type; 

 and that the ova of the variety will reproduce not only this, 

 but also more or less aberrant perfect individuals. An inva- 

 riable, fixed and constantly-recurring ornamentation in any 

 group of perfect beings, except when it is a mere intensity or 

 pallidness of hue, which will but rarely mislead, is not only 

 incompatible with the conception of a variety, but would con- 

 stitute a true species, even when their biographies are closely 

 coincident. Variation, or specific instability, observing fixed 

 and determined limits, which must be ascertained by obser- 

 vation, is part of the true history of species. It is not 

 manifested to the same degree, probably, in the specific life 

 of every true species, but wheresoever and whensoever it 

 does occur is capable of being referred to its normal type, by 

 its agreement in all those essential characteristics necessary 

 to form a conception of true species. As long as the specific 



