552 British Association for the Advancement of Science. 



sobs recovers ; whilst if it is suspended for a minute the animal irre- 

 coverably dies. — The Chairman observed that he had often dried to 

 powder the eggs of various insects, which having been put into water 

 were hatched. 



Mr. Golding Bird referred to the observations of Mr. Gray, with 

 respect to the production of insects, as stated by Mr. Crosse in his 

 experiments, which he had repeated on a large scale, but without 

 any result, although he had continued them for some weeks, varying 

 them in every possible form. He also explained that such could 

 not have been produced from the silica, as this was precipitated from 

 the mixture of the alkaline solution of silica and muriatic acid, the 

 fluid passing through the filter being nothing but very dilute mu- 

 riatic acid. 



Sept. 12. — The President observed that he was about to read 

 a letter upon a subject that had excited some interest in the scien- 

 tific world, on account of the difference between two eminent 

 naturalists, — Mr. Thompson and Professor Rathke, of Berlin. He 

 remarked, that at first sight it appeared strange, that animals ap- 

 parently so high in the scale of organization as the crabs and lobsters 

 should undergo the same changes in the course of their develop- 

 ment, as the class Insecta. Mr. Thompson had observed, that the 

 young of the barnacle shell were deposited by the parent in a free state, 

 and that they afterwards became fixed 5 and the same fact had been 

 pointed out to him by that zealous naturalist Mr. Darwin. It was 

 therefore not extraordinary Mr. Thompson should take the view he 

 did of the development of Crustacea. The letter he had on this sub- 

 jectwasfrom Capt.DuCane, of Southampton, who, from his contiguity 

 to the sea, had been led to investigate this subject. He had obtained 

 the ova of what he supposed to be the common prawn : after keep- 

 ing them in water a little time, they produced a number of minute dia- 

 phanous animals, altogether different from the full-grown prawn. 

 These ova were obtained from a ditch open to the influx of the sea, 

 but the water was only slightly brackish. Captain Ducane therefore 

 proposed to call this animal the " Ditch Prawn." The letter was ac- 

 companied by a drawing, exhibiting the various changes which the 

 Captain had observed to take place in these animals during the first 

 three days after their leaving the ova, none of his specimens living a 

 longer period. 



The President observed, that the subject of the development of 

 Crustacea was a most interesting subject. He questioned whether 

 many of the received species of that class were anything more than 

 one animal in its several stages of development. 



Dr.Richardson inquired if it might not be possible for Capt. Du Cane 

 to have mistaken some parasitic animals for the young of the prawn. 

 The Rev. F. W. Hope was inclined to think the animal alluded to be- 

 longed to the shrimp, and not to the prawn family. On the Norfolk 

 and Suffolk coast, the ditch shrimp was common. He believed crus- 

 taceous animals themselves were frequently parasitic. — The President 

 replied, that the ova obtained by Capt. Du Cane were too abundant 

 to be the produce of a parasitic animal, and the results too constant 

 to lead to such a supposition. 



