31 



said that a partridge had visited his garden at Holloway 

 quite recently, and that the pied blackbird had for the 

 fourth season returned to his garden to breed. Last 

 year the brood contained two young which were splashed 

 with white. He exhibited specimens of parasitic Hymen- 

 optera. 



Mr. F. Noad Clark exhibited slides of Desmids which had 

 been prepared by Professor Bryan's method, as described in 

 " Science Gossip " last year (igoo). They included several 

 species of Micrasterias, Closteriuui, Cosmarium, Peniuvi, etc. 

 The colour and outline of these were seen to be perfectly 

 preserved, a result which is generally difficult to attain with 

 this class of object. Mr. Clark expressed the opinion that 

 these mounts were as nearly as possible permanent. 



Mr. R. Adkin, referring to the Acherontia atropos exhibited 

 by him at the last meeting, said that he had opened several 

 of the pupae from which the imago had not emerged, and 

 found them hollow sacs, but in some there were remains of 

 a membrane. 



Dr. Chapman remarked that the great cavity shown in 

 the abdomen of the imago of atropos might, perhaps, be 

 stretched in drying, but represented substantially the air 

 cavitiesformedby dilated tracheae, which occupy much space 

 in the abdomina of so many insects. Inflation of these 

 cavities, and apparently also of portions of the alimentary 

 canal, was a constant resource at emergence from the pupa 

 to secure the tension and increased bulk necessary for 

 rupturing the pupa case and cocoon, as also to obtain ten- 

 sion of the cutaneous envelope, and so fulcra for muscular 

 action, — as, for example, in male Psychids at pairing time, 

 and in female Psychids in completing oviposition. In the 

 case of atropos these large cavities, compressed by muscular 

 action, afforded the means of making the squeak of that 

 species. At the base of the proboscis was a sac or space, 

 apparently a dilated portion of the upper extremity of the 

 oesophagus ; between this and the proboscis was an opening, 

 capable of being contracted to a narrow slit, a truly laryn- 

 geal structure. Air forced out of the sac through this slit 

 produced the squeak. Some similar structure probably 

 exists in all Lepidoptera that have suctorial habits, and 

 forms a pump for sucking up through the proboscis and 

 passing the results onwards. It has no sufficient muscular 

 apparatus, but is largely surrounded by dilated tracheal 

 vessels. There seems, therefore, to be present no means of 

 forcing air (or other fluid) into or out of this vocal and 



