SECTIONAL TRANSACTIONS.— U. 363 



The specimens, including some sixty animals or parts of animals used in medicine, 

 are thus close on 200 years old. 



It has long been realised that museums impart knowledge with a precision ami 

 vi\'idness wliich no mere literary description can give. These old Oxford collections, 

 though few in number and diminutive in size, were made by the pioneers of the 

 premier educational method of the science museum. They alone of many larger 

 collections that have been destroyed now illustrate the early history of museums in 

 Great Britain. Their adequate exhibition to the public in our own time, and a 

 guarantee for their preservation for study by future generations, are therefore matters 

 of paramount importance. Members of the British Association are invited to inspect 

 them in the oldest public museum of natural history, in the Old Ashmolean building 

 in Oxford. 



Department I.* 

 • Section divided. 



1 1 . Dr. A. J. Grove and Mr. L. F. Cowley. — On the Secretion of the 



Cocoon in Eisenia foetida, the Brandling Worm. 



The freshly deposited cocoon of E. foetida consists of (1) an enveloping transparent 

 mucilaginous slime-tube, (2) a semi-transparent cocoon membrane, and (3) the 

 albuminous contents. 



Grove {Q.J.M.S., vol. 69, 1925, p. 274) described in the clitellum of L. ieirestri-s 

 three different kinds of glandular elements. In E. foetida the same three kinds of 

 glandular elements have been distinguished, and by differential staining of sections 

 of worms killed during the process of cocoon formation it has been possible to 

 demonstrate that the three glandular elements produce respectively the three eorr- 

 stituents of the cocoon. Thus the slime-tube is produced by the mucin cells ; the 

 cocoon membrane by the large granule glands ; and the albuminous contents by the 

 deep-seated fine granule glands. 



12. Mr. B. N. ScHWANWiTSCH. — Evolution of Wing-pattern in ButterfHen . 



13. Dr. 6. D. Hale Carpenter. — Mimicry in Relation to Geographical 



Distribution in the Ethiopian Nymphaline Butterfly ' Pseudacrcea 

 eurytus.' 



Pseudacrcea eurytus was known to Linnaeus in 1758. The type has a simjjle pattern, 

 very dark brown and orange in the male, black and white in the female. It belon<»s 

 to a genus related to the ' White Admiral,' and frequents forested or thickly bushed 

 country : the flight is floating and the butterfly shy. 



Numbers of butteiflies have been described as species of Pseudacrcea, sometimes 

 with sexes alike, sometimes with sexes so different that males and females wero 

 described as distinct species. Li 1912 breeding confirmed what was suspected om 

 anatomical grounds, that the majority of ' species ' of Pseudacrcea are forms of one 

 species (eurytus) found throughout the forested country in Africa from S.W. Abyssinia 

 on the north to Pondoland in the south, and from the west coast to Mombasa. This 

 note is intended to direct attention to an exhibit of forms assumed by this remarkably 

 polymorphic species, whereby the public for the first time can realise the diversity- 

 induced by the appearance of other species not closely related. Every form of 

 eurytus shown resembles an Acraeine butterfly of genus Planevia, sex for sex. Where 

 the Planema has sexes alike the Pseudacrcea is monomorphic ; where the Planema 

 is dimorphic Pseudacrseas are found each resembling the appropriate sex of a Planema. 

 On certain islands of Lake Victoria, when Planemas were scarce, forms of euri/tui 

 abounded showing variations transitional between the usual well-marked forms. The 

 interpretation of these facts is that the Planemas, belonging to a sub-family known 

 to be distasteful to insectivorous vertebrates, are copied by the Pseudacrseas. The 

 former are termed ' Models,' the latter ' Mimics.' 



Mimetic resemblance is produced by natural selection working on tho variations 

 of eiirytus. In the presence of Planema those variations have the best chance of 

 surviving which most closely resemble the models. 



