816 Proceedings of the British Association for 1850. 



been employed for the same purpose. — Other plants used for 

 hedges are Pandanus odoratissimus, the lime, the mulberry, 

 species of Hibiscus, &c. The paper was illustrated by draw- 

 ings of the species of plants described by the author. 



" On Exuviation, or, the Changes of Integuments by Ani- 

 mals," by Sir J. G. Dalyell. — The observations of the writer 

 were confined to the family of Crustacea. He described mi- 

 nutely the changes undergone by crabs during the process of 

 moulting, and, in several instances, counted the number of 

 days from one moult to another. These varied from 60 to 194 

 days. In all cases he found that no reparation of wounded, 

 mutilated, or destroyed parts took place till after the moult 

 which succeeded the injury. He described minutely several 

 cases in which injuries of various kinds had been repaired. 

 In one case of the moult of a crab only the two claws of the 

 dermal skeleton were developed, whilst the eight legs were 

 entirely suppressed. At the next moult the animal pro- 

 duced its usual number of legs. 



Professor Owen wished to express the obligations under 

 which naturalists were to Sir J. Dalyell for his numerous 

 observations in natural history. The subject of the present 

 paper was one of great interest and demanded further inves- 

 tigation. — Professor Van der Hoeven stated that the remarks 

 of Sir John confirmed those of Mr Newport on the cliange 

 of skin and the reproduction of lost members in the family 

 of spiders. — Mr Peach said that the white colour of the 

 young crabs mentioned by Sir John was owing to confine- 

 ment. He believed that limbs were only reproduced after 

 exuviation, from his own observations. Amongst the 

 Crustacea which he had observed, the hermit crabs shed 

 their skin most frequently : — sometimes as often as five or 

 six times in a month. 



" Notes on Crustacea, accompanied by Drawings," by Dr T. 

 Williams. — The notes were, first, — on the development of the 

 shell. Under this head the author gave an account of the 

 changes observed in the shell during its growth when exa- 

 mined by the microscope. In the first place a production of 

 cells was observed over the region of the heart. This gradual- 



