180 SUMMARY OF CURRENT RESEARCilES RELATING TO 



conditions of life — in orchid-houses — have brought about the simplifica- 

 tion of the life cycle, the permanence of the " aleurodif orm " stage. 

 The insect is probably one of the migratory Aphides that has been 

 deprived of the series of metamorphoses, owing to an artificial mode of 

 life. Experiments should be made on Hormaphis hamamelidis, or on 

 some other migratory Aphis, with a view to ascertaining whether — by 

 affording successive generations a constant supply of food under equable 

 conditions of temperature, etc.- — the creature could be maintained for 

 many generations, or permanently, in the aleurodif orm stage. 



Maturation in Viviparous Aphides.* — J. P. Stschelkanovzew has 

 studied the phenomena of maturation in the summer ova of Aphis rosrc, 

 showing that only one polar body is formed. The changes in the 

 chromatin-substance occur very rapidly and in somewhat simplified 

 fashion. The old chromatin thread of the germinal vesicle is partly 

 dissolved, and probably gives rise to several of the nucleoli, though the 

 majority of these arise by new formation. During the formation of 

 the nucleoli, changes occur in the plasma of the ovum, apparently 

 implying a passage of chromatin-like substance from the plasma into 

 the nucleus. The new chromatin thread from which the chromosomes 

 of the polar body arise, is formed directly from the peripheral nucleoli, 

 and shows no trace of a longitudinal splitting. The chromosomes show 

 marked differences in size. 



Neapolitan Myrmecophilous Insects, f — F. Silvestri describes the 

 myrmecophilous habits of Tettigometra impressifrons Muls., and T. 

 costulata Fieb. (Hemiptera), Hyperaspis reppensis Herbst. (Coleoptera), 

 Mprmeeophila acervorum Panz., and M. ochracca Fisch. (Orthoptera). 



Genealogical Study of Dragon-fly Wing Venation. J — J. Gr. 

 Needham seeks to translate the records of natural selection as written 

 in the venatioual characters of Odonate wintrs. The result is a most 



m o 



interesting essay on " developmental dynamics," showing how in accord- 

 ance with mechanical principles, .operating in vein-shifting and vein- 

 differentiation, a form of wing is reached, several times independently, 

 that is most efficient, — a wing broad at the base and long and pointed at 

 the apex, rigid at the front and pliant toward the posterior margin — a 

 wing combining the principle of the aeroplane with that of the scull. 

 But this is only a hint of the scope of an elaborate and suggestive 



investigation. 



B. Myriopoda. 



Littoral Myriopods.§ — F. Silvestri records from the shore of Portici 

 near Naples, six Myriopods, namely, Pachymeriumferrugineum C. Koch, 

 Geophilus poseidonis Verb., Henia bicarinata (Mein.) Silv., and Scliendgla 

 submarina Grube, among Chilopoda ; and Polyxemis lapidicola Silv. 

 and Isobates littoralis Silv., among Diplopoda. It seems that littoral 

 Myriopods are much more frequent than is generally supposed, but the 

 author distinguishes (a) accidental halophilous forms (three species of 



£■;■ * Biol. Centralbl., xxiv. (1904) pp. 104-12 (7 figs.). 



t Ann. Mns. Zool. Univ. Napoli, new series, i. No. 13 (1903) 5 pp. 

 J Proc. U.S. Nat. Mus., xxvi. (1903) pp. 702-64 (24 pis. and 44 figs.). 

 § Ann. Mns. Zool. Univ. Napoli, new series, i. (1903) No. 12, 5 pp. 



