1895- RESULTS OF '' CHALLENGER'' EXPEDITION. 6i 



microscopic sections of some of the insects, published a short descrip- 

 tion [Zool. Anz., X., 1877, p. 336) of their internal anatomy. Finding 

 organs normally belonging to the abdomen situated in the thorax, 

 and modifications for an aquatic life carried to the most extreme 

 point, he naturally regards Halohates as a most aberrant type of bug. 



Dr. F. Dahl has recently described " Die Halobatiden der 

 Plankton Expedition " (Ergebnisse der . . . Plankton Expedition 

 der Humboldt-Stiftung, ii. g., 1893), from the N. Atlantic, separating 

 one specimen as the type of a new species. Other species of Halobates 

 have been described by Mr. F. Skuse {Rec. Austral. Mus., i., i8gi, 

 p. 174), Dr. E. Bergroth [Revue d'Ent., xii., 1893, P- 204), and the 

 writer of this note (Sci. Proc. R. Dubl. Soc, vii., 1892, p. 144). 



Observations on the habits of Halobates have been lately 

 published (Ent. MontJdy Mag., 2, iv., 1893, pp. 227, 252) by Mr. J. J. 

 Walker, R.N. He notes that while the insects remain on the surface 

 during calm weather, or in a swell without wind, they disappear 

 "with the ripple caused by the slightest breeze." Observing also, 

 that specimens kept in a vessel of sea-water dive on the approach of 

 a foreign body, and swim readily beneath the surface, he concludes 

 that it is their habit to dive into still water whenever the surface is 

 disturbed. 



In the "Challenger" Report, Dr. White transferred several 

 insects of doubtfully pelagic habit, referred by older authors to 

 Halobates, to a new genus Halobatodes. Dr. F. Meinert {Ent. 

 Meddelelser, i., 1887, p. 140) regards these as individuals of the fresh- 

 water genus Metrocoris, Mayr, in which the wings have not been 

 developed. Mr. Walker found these insects in harbours and estuaries. 

 They are of considerable interest, as representing a transition 

 between the (usually) winged, freshwater Hydrometridae and the 

 wingless, oceanic Halobates. The ocean is believed to have been 

 the original cradle of all animal life, but its most gigantic inhabitants, 

 the " great whales," and these small and humble insects must be 

 regarded as modified land-animals driven back from the crowded 



continents to find a home in its waters. 



Geo. H. Carpenter, 

 mollusca. 



As regards the Molluscs, the " Challenger " Expedition has 

 made known a very large number of new marine forms, both genera 

 and species, belonging to the different classes. But, from the point 

 of view of pure zoology, all these forms are not of equal interest. We 

 must, therefore, limit ourselves here to the chief of those whose study 

 has yielded results of morphological importance or led to notable 

 conclusions in phylogeny. From this point of view the following facts 

 may be indicated as the most important : — 



I. Among the peculiarities of organisation in abyssal molluscs, in 

 relation to the conditions of their existence, there has been described 

 the disappearance of the cephalic eyes in various Gastropoda (a fair 



