212 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tbeso spaces have proper walls. A certain change may be observed in 

 the morphological appearance of the secreting organs of one and the 

 same species, and this is dependent on the active or passive condition of 

 the cell. The hemipterous species Pyrrhocoris apterus, the dipterous 

 Musca domestica, Homalomyia canicularis, Calliphora erythrocephala, 

 Lucilia sp., Etistalis arbustorum, E. tenax, &c, were also examined. 



Sense of Direction in Formica rufa.*— Dr. II . C. M'Cook gives an 

 account of his observations on the structure of the ant-hills, and the 

 character of their roads and engineering skill in Formica rufa, as seen 

 in the Trossaehs of Scotland. He finds that the ants showed an accurato 

 sense of direction in marking out and following their approaches to the 

 trees. It would be scarcely possible to attribute such mathematical 

 accuracy as they exhibit to mere accident. The roads were as accurately 

 laid down as ordinary roads made by the engineering skill of man. 



This skill in the ants was all the more apparent from the fact that 

 their paths were carried through a jungle of bracken and other plants. 

 No facts were obsorved which justify speculation on the manner in which 

 this feat of engineering was accomplished. Sentinels stationed near the 

 ant-hills exhibited great alertness; the finger of Dr. M'Cook was ob- 

 served at about an inch or an inch and a half s distance ; the sentinels 

 thrust out their antennae, extended their heads, then their front legs, and 

 finally the middle legs, while the abdomen was slightly turned under- 

 neath the body, as though prepared to eject formic acid on any adversary. 



Respiration of Hydrophilus.t — Herr v. Fricken describes the mode 

 of aquatic respiration in Hydrophilus aterrima, Hydrocharis caraboides, 

 and Piceus. He saw that thoy store up the air, not under the wing- 

 covers, but in the hairy covering of the under surface. The air is caught 

 and renewed, not as in Pytiscus by raising the posterior end of the 

 body above the surface of the w r ater, but, as Nitsch recorded, by forming 

 a small whirlpool by means of the antennas, the first joint of which pro- 

 jected above the surface of the water. 



Aorta of Bombyx mori.J — Signor S. Selvatico finds in Bombyx mori, 

 as Burgess has observed in other Lepidoptera, that the aorta is bent 

 anteriorly and widened out into a kind of chamber, which has about the 

 form of an equilateral triangle, with the apex directed downwards ; from 

 the basal angles two vessels are given off, one of which goes to the optic 

 ganglion and eyes before opening into the lacunar passages ; the other 

 extends all along the interior of the antennas. At the base of the 

 antennas the vessel widens, and contains a peculiar spherical structure, 

 which is attached to its wall by special fibres; this is apparently an 

 apparatus for closing the lumen of the vessel. The author draws 

 attention to the fact that in Bombyx mori the supra-intestinal nerve passes 

 into the interior of the aorta and extends some distance along its lumen. 



Larva of Culex.§ — Herr E. W. Easchke gives a careful and detailed 

 account of the anatomy of the familiar larva of Culex nemorosus. While 

 useful as a sufficiently exhaustive account of a form which has not been 



* Proc. Acad. Nat. Sci. Philad., 1887, pp. 335-8. 



t Biol. Centralbl., vii. (1887) pp. 633-4. (60 Versamml. Deutsch. Naturf. u. 

 Aeizte.) 



X Zool. Anzeig., x. (1887) pp. 562-3 ; also in Pubblicazioui 11. Statione Bacologica 

 Sperimentale (Padova) 1S87, 19 pp., 2 pis. 



§ Arch. f. Naturgesck., liii. (1887) pp. 133-63 (2 pis). 



