360 SECTIONAL TRANSACTIONS.— D. 



impurities known to be present in or on the foliage of plants in manufacturing districts. 

 Both, methods were adopted, the species used being Selenia bilunaria Esp., Tephrosia 

 bisiortata Goeze and T. crepuscularia Bkh., and the salts manganese sulphate and lead 

 nitrate. Small numbers of melanics appeared in all the experimental cultures, and 

 the melanism so induced proved to be inherited as a Mendelian recessive in the case 

 of 8. bilunaria and T. hislorlata and as a dominant in T. crepuscularia. 



The results are of extreme importance from an evolutionary point of view by- 

 demonstrating that the germ-plasm can be affected by environmental influences. 

 In addition they afford a ready explanation of the origin of local races, of the evolution 

 of closely allied species of insects with distinct food-plasts, of the break of domestic 

 animals and plants into distinct breeds, and of other similar occurrences. 



" 3. Dr. H. Eltringham. — Butterfly Vision. 



The structure and function of faceted eyes. The Mosaic theory of ineect vision. 

 Pseudocone and eucone eyes. Exner's explanation of the action of the compound 

 eye. The superposition and apoposition images. The Glow-worm's eye. The eyes 

 of Flies and Dragon-flies. The structure and action of the Butterfly's eye. Its 

 erect image. Can Butterflies distinguish colours ? Description of experiments 

 designed to solve this problem. The question of ultra-violet light. Conclusions. 



4. Prof. \V. C. McIntosh, F.R.S. — The Structure of the Operculum, in 



Mercierella and allied forms. 



The peculiar aspect of the operculum of Mercierella, which at first sight suggested 

 opercular development, led to the following inquiry in specimens provided by ilr. 

 Carmichael Munro, of the British Museum, from a series sent by Mr. Charles Major, 

 on whose barge they occurred. In the original account by Prof. Fauvel no allusion 

 to the internal structure was made, nor was this dealt with in Mr. JIunro's remarks 

 on the British form. 



In Prof. Fauvel's subsequent remarks the masses of blood contained in the 

 operculum were considered to be mucus. The present inquiry shows that the 

 operculum and its stalk in Mercierella have a chitinous layer externally, then a layer 

 of hypoderm which thins off as the operculum is reached, whilst internally the centre 

 of the stalk has the blood-vessel and a series of fine reticulations which somewhat 

 increase in size as they approach the operculum, in which they enlarge into great 

 blood-spaces. The blood, which is greenish in most Serpulids, readily forms isolated 

 masses which stain deeply. The opercular stalk, which is morphologically a branchial 

 filament, is contrasted with these organs and the modifications demonstrated, as well 

 as the presence of remarkably elongated terminal processes to each filament. The 

 structure in Mercierella is then compared with that in various Serpulids such as 

 Ficopomatus, Hydroides, Serpula vermicitlaris, Pomatocerus, Spirorbis and others in 

 which an approach to the condition in Mercierella occurs, and the importance of the 

 operculum in relation to the circulation, and perhaps in certain forms to respiration, 

 indicated. 



The new British Polychaet which was sludged by Prof. F. J. Cole, of Bristol, 

 near Port Erin in the Isle of Man, is closely allied to Anicea trilobata, one of the many 

 discoveries made in northern waters by the elder Sars: but whilst agreeing in general 

 structure with this species, it presents certain divergencies — if the descriptions and 

 figures of Malmgren can be relied on. Thus the oval folds form dorsally a deep frill 

 which curves ventrally on each side to form two parallel flaps that pass outward 

 in front of the first segment as large lamellae beset witli numerous small tentacles as 

 in the type. In A. irilokafa, instead of the frill, a median tongue-like process occurs 

 on the ventral surface, the anterior edge of the dorsal collar is smooth, and a simple 

 transverse segment lies behind the lateral lamellae, whereas in the British form there 

 is a thick curved arch or ridge. Moreover, instead of the median groove anteriorly 

 on the ventral surface of the British form, there are five scutes in the Norwegian. 

 The bristles, so far as they occur in the injured example, agree with the type. 



5. Reports of Committees. 



6. Dr. F. A. DiXEY, F.R.S.— iecfwre on Recent Criticisms of the Theory 



of Mimicry. 



