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character which must be counted as of the greatest importance, inas- 
much as it admits of no exceptions. This character is the position of 
the apertures of the generative organs. In the Pauropoda and Diplo- 
poda (Millipedes) these apertures are situated near the anterior end ofthe 
body between the second and third pairs of ambulatory legs. In the 
Chilopoda (Centipedes) and Symphyla (Scolopendrella) on the contrary 
they are placed at the posterior end of the body in close proximity to 
the anus. Now in the Hexopoda the generative organs open exactly 
as in the two last-named sections of the Myriopoda, a fact which at once 
suggests the idea that these three groups are nearly allied to each other. 
And this idea is fully borne out by the circumstance already frequently 
pointed out by Menge, Haase, Grassiand others, that Scolopendrella is 
closely related to those less specialised apterous Hexopods that are known 
as Thysanura!. No one in fact who compares a Scolopendrella with 
a Chilopod on the one hand and with a Thysanurous Hexopod on the 
other can avoid being struck by the fact that the differential characters 
between the Insects and the Centipedes are to a large extent bridged 
over, and that Scolopendrella must consequently be regarded as the 
living form that comes nearest to the hypothetical ancestor of these 
two great divisions of the Tracheate Arthropoda. 
On the whole, however, it would seem that its affinities are rather 
with the Chilopoda than the Hexopoda, for the reason that the latter 
have obviously departed more from the primitive ancestral type than 
the former have. 
This conclusion, however, is not a new one as has been stated 
above. But previous authors, with the exception of Mr. J.S. Kingsley, 
when discussing the phylogeny of Insects and Myriopods have mostly 
spoken of the latter as a natural group, equal in value to and to be con- 
trasted with the Hexopoda. The adoption of such a classification in 
works bearing upon a subjet like phylogeny, implies seemingly a belief 
on the part of those who employ it, that the component orders of the 
Myriopoda are more nearly related to each other than any of them are to 
the Hexopoda. That such, however, is in reality the case, I find it 
impossible to believe, in the face of the singular difference afforded by 
the situation of the genital orifices. This character it seems to me is of 
far greater importance as a sign of distinction than the points of resem- 
blance, which Mr. Wood-Mason? has attempted to trace between 
Scolopendrella and the Chilognatha, are as signs of relationship. 
If this opinion is well founded and the conclusions that follow 
1 Packard goes so far as to associate this genus with the Thysanura. (Am, 
Nat. XV. p. 698. 1881.) 
2 Ann. Mag. Nat. Hist. XII. p. 53 ete. (1883.) 
