174 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
there has been a reduction of the true membranous anterior wings of 
Coleoptera. It may be that alulae and wing-covers of Dytiscidae on the 
one hand, anterior wings and tegulae of Hymenoptera on the other hand, 
have a common origin, and have arisen either by unequal growth from 
the first, or by subsequent reduction (in association with disuse) of both 
tegulae and alulae. The hypothesis would at least explain many dif- 
ficulties. 
Biological Import of Genital Appendages.* — Herr C. Escherich 
begins his essay with a general survey of the genital appendages in 
different orders of insects. He distinguishes in the males a primary 
part, the chitinous tube around the ductus ejaculatorius, from the 
secondary parts, protective and clasping. He describes uni-, bi-, tri-, 
and quadrivalvular forms of the copulatory apparatus. In the second 
part of his essay, the author shows how remarkably precise a criterion 
of species is furnished by the nature of the genital appendages. This 
is true of both sexes. In the third place he maintains that fertile 
sexual union can take place only between those forms whose genital 
appendages accurately correspond. Hybridism between different species 
seems mechanically impossible. The author does not think that the 
intricacies of the copulatory apparatus can be readily interpreted as 
adaptive. He invokes the aid of das Princip der Keinerhaltung der 
Arten. This, he believes, is the final cause ; but the efficient cause is 
ein unbeJcanntes Kraft. 
Dichogamy of Lepidoptera.f — Herr W. Petersen believes that the 
advantage of dichogamy lies in the prevention of in-breeding. He 
would call it, we know not why, “ dichogennesis,” and finds that it 
presents a striking analogy with dichogamy in plants! We should 
think that this was somewhat obvious. He believes that its occurrence 
may be readily accounted for by natural selection. The value of the 
paper is not in its biological considerations, which are commonplaces, 
but simply in its statement of the actual cases in which Lepidoptera are 
dichogamous. 
Phylogeny of Papilionidae f— Herr A. Spuler believes that Lepi- 
doptera have arisen from forms resembling Neuroptera, and that they 
present in the structure of their wings a close resemblance to Tri- 
choptera, though they are not derivable from any forms like those now 
living; nor are they of monophyletic origin. In ontogeny there is a 
uniform type of venation — the sub-imaginal stage. In regard to veins 
and scales, the species of Thais are more primitive than other Equitidae. 
From Thais-like ancestors the main stem of Papilionidae and Parnassiae 
has arisen, and the Pieridae also have had similar ancestors. In the 
Equitidae (especially in the Rhopalocera, and certainly in many Hete- 
rocera) there are congruent markings on both pairs of wings, identical 
on both upper and lower surface, and referable to transverse unions of 
spots. In all Equitidae the markings are traceable to one original type, 
though not necessarily to one original species. Herr Spuler has con- 
structed a very elaborate genealogical tree. 
* Yerh. Zool.-Bot. Ges. Wien, xlii. (1892) pp. 225-39 (1 pi.). 
f Zccl. Jahrb., vi. (1892) pp. 671-9. \ Tom. cit., pp. 465-98 (2 pis.). 
