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assumption of a similarity rooted in community of origin. On the 
contrary, as he considers absence of colour to be the primitive 
condition in Diptera, he believes in “the probability of an independent 
origin of colour in many different points of the group, because we 
meet coloured wings in so many and such different families.” 
But though he thinks that these different colour-patterns have 
arisen independently of each other, he accepts a connection between 
them in so far that he believes special regions of predilection for 
colour-formation to be indicative. These regions being either the 
nervures themselves, or the spaces between these nervures, his 
observation may be regarded as confirmation of my opinion, that 
the colour pattern is originally bound to the nervural system. The 
same may be said of the evident predilection for pigment-accumulation 
along the wing-margins and at its root. 
I likewise fully agree with pe Meyere, where he ascribes the 
formation of coloured transversal bars in many cases to the 
broadening of colour-seams along transverse veins, as well as when 
he attributes the cloudy “fumigation” of wing-areas to an extension 
of spots or blotches (which therefore originally must have been 
smaller). , 
All these pbenomena may be considered as manifestations of the 
different manner, in which an original pattern can become modified 
and differentiated. The same is the case with the transformation of 
spots into transverse stripes, or the coalescence of two spots on 
either side of a nervure into one single blotch, which consequently 
will become divided by the vein. 
The final proof that the more complicated patterns on coloured 
Dipterous wings may justly be considered as differentiations of one 
common primitive design bearing a simpler and more regular 
character, can only be obtained by showing that the formation of 
the definite pattern is preceded by the temporary presence of a 
preliminary pattern, possessing the above mentioned more primitive 
character; that is the same proof as I was able to obtain for 
Lepidoptera. But in expectation of this ontogenetic proof, it is 
allowable to heighten the probability of the supposition by adducing 
arguments founded on the comparison of fullgrown forms, which 
in the mean time may furnish us with a reliable image of this 
primitive pattern. For this purpose we have to start from the 
comparison of species belonging to the same genus, or to nearly 
related genera, and, having come to a conclusion about their 
ancestral form, to compare this with a similar one of various genera 
belonging to another family. 
