SCIENTIFIC SOCIETIES. 149 



representatives of segraentally disposed glandular organs may be said to 

 occur throughout the length of the Hexapodan body. In the discussion 

 which followed, Mr. A. R. Hammond referred to the saccular reservoir on 

 the ventral surface of the prothorax of the larva of the Puss Moth, Cerura 

 vinala, from which an acid fluid is said to be ejected ; also to the large 

 pear-shaped glandular cells which underlie the integument of the thoracic 

 segments in the larva of Dicranota bimaculata, as described by Prof. 

 Miall (Trans. Entom. Soc. 1893, p. 235). The function of these cells 

 appeared to be the secretion of an oily fluid. 



In the second paper by Prof. Gilson and M. J. Sadones— " On the Larval 

 Gills of Odonata" — the authors described in each branchial lamella of 

 Libellula depressa three conical processes which are functional in preventing 

 adherence of the lamella to its fellows, and in maintaining full exposure to 

 the surrounding medium. The authors showed that the tracheal ramifica- 

 tions are looped tubules running parallel with the surface of the gill, which 

 at all points lie embedded in a subcuticular protoplasmic syncytium. Stress 

 was laid upon the fact that the in- and out-going tracheal tubules are related 

 to one and the same branchial main tracheal trunk, and that the air within 

 the gill does not circulate regularly through the tracheal system. Turning 

 to physiological considerations, it was pointed out that gaseous interchange 

 between the contents of the gill-lamina3 and the surrounding medium must 

 of necessity take place through the living protoplasm of the lamellar syn- 

 cytium ; and, on consideration of the fact that the death of an epithelium 

 is known to profoundly alter the osmotic properties of the tissue which it 

 composes, the conclusion was drawn that absorption of oxygen must here 

 involve something more than a mere physical process. Attention was then 

 directed to the existence of a "prse-rectal vesicle" from which there depend 

 into the lumen of the guts a couple of epitheloid disks. It was suggested 

 that this structure, together with a similarly differentiated epithelium lying 

 about the bases of the gills, might be possibly concerned in the removal of 

 carbonic anhydride. The authors accordingly discriminated between the 

 air-vascular (tracheal) system, as concerned in the absorption and dissemina- 

 tion of oxygen, and the blood-vascular as concerned in nutrition and the 

 removal of waste. In the discussion which followed, Mr. A. R. Hammond 

 expressed his satisfaction at finding that the authors' observations on the 

 gills of Odonata confirmed to some extent his own views as to the syncytial 

 condition of the hypodermis in aquatic larvae. In the larvae of the red- 

 blooded species of Chironomus this condition appeared to be most strikingly 

 exemplified. 



March 19th. — Mr. C. B. Clarke, F.R.S., President, in the chair. 

 Messrs. James Backhouse and Spencer H. Bickham were admitted, and 

 Messrs. J. H. Leigh and Edward Step were elected Fellows of the Society. 

 Mr. Thomas Christy drew attention to the fact that the Anniversary 



