Linnctan Society. 291 



with Etheria, from which it appears only to differ in the very small 

 size, or indeed in the total absence of the anterior adductor muscle. 

 Like Etheria^ the lower valve is rather attached to the stones and 

 shells to which it is affixed, by inequahties in the form and surface 

 of the shell, than by any real attachment of the substance of the shell 

 itself, for the attached valves are covered with a continuous periostraca. 

 As all attached shells have a free young state, as may be seen by 

 examining the umbones of Arcinella, Chama, and other attached bi- 

 valves, the young of Etheria are doubtless free, and there is nothing 

 peculiar in the young of Mulleria being free ; but there is a great 

 peculiarity in the young shell becoming united into a tubular case, 

 and one of the valves, after the other has become attached, separating 

 itself from its younger part by a natural caries or crack. 



LINN^AN SOCIETY. 



February 6, 1855. — Thomas Bell, Esq., President, in the Chair. 



Mr. Westwood, F.L.S,, exhibited some cocoons and living chry- 

 salides of the Eria Silk- worm of India, which feeds on the castor-oil 

 plant, which he had received from the Governor of Malta through 

 Dr. Templeton ; this being the species, the introduction and culti- 

 vation of which in Malta, Italy, and the South of Europe was now 

 attracting so much attention in those countries, as proved by the 

 numerous communications presented within the last few months to the 

 Academic des Sciences at Paris by Marshal Vaillant, French Minister 

 of War, and by MM. Milne-Edwards, Guerin-Meneville, Isidore 

 GeofFroy Saint- Hilaire, Dumeril, Montagne, &c. An extract was 

 read, communicated by Major-General Hearsey, from the " Journal 

 of the Asiatic Society," on the peculiarities of the silk of this species, 

 the natural history of which, as well as of the Tusseh Silk-moth of 

 India, formed the subject of an excellent memoir by Dr. Roxburgh in 

 the " Transactions of the Linnsean Society," vol. vii. On examining 

 the cocoons, Mr. Westwood had observed, that, unlike those of the 

 common Silk-worm and most other moths which were of an entire, 

 oval form, these cocoons were open at one end, which was protected 

 by a series of converging elastic threads (like the mouth of a rat-trap), 

 a peculiarity which had been long observed in the cocoons of the 

 common Emperor Moth, Saturnia pavonia minor. This peculiarity, 

 which had also been noticed by M. Dumeril, had been supposed to 

 have for its object the introduction of air to the interior of the 

 cocoon, and also the prevention of the ingress of parasitic Ichneu- 

 monidce, &c. Neither of these hypotheses were however considered 

 by Mr, Westwood as conclusive ; he thought rather that it was con- 

 nected with the discharge of the fluid which most insects emit im- 

 mediately after arriving at the perfect state. The circumstance is 

 however of some practical importance in the Eria Moth, as it allows 

 the egress of the perfect insect without injuring the thread of the 

 cocoon, as is the case when the common Silk-worm Moth of the 

 mulberry is allowed to escape from its cocoon. It is not, however. 



