68 Miscellaneous. 



i. e. in tlie substance of the lamellae forming the pulmonary sacs, 

 thence it is brought to the heart by particular vessels. In the other 

 two groups the same holds good, except that the vascular system is 

 of a higher grade than that of insects. 



What do we find, says IVI. Blanchard afterwards, in higher animals, 

 where the respiratory organs are localized ? We always find that the 

 blood gets into contact with the air by circulating in the lamellae 

 forming the pulmonary or branchial sacs ; now, in those animals in 

 which the respiratory system is disseminated throughout the body, 

 by means of tracheae, ought not the law to remain the same ? The 

 pulmo-tracheary Arachnida furnish, in this point of view, a valuable 

 intermediate stage. The pulmonary sac is prolonged in the form of 

 minute, very slender tubes, which are true tracheae ; now if the blood 

 circulates between the two laminae of the vascular sac, it is probable 

 that it also circulates between the two laminae of the trachea, and 

 must not the same thing occur in those Arachnida which are solely 

 tracheary ? M. Blanchard has confirmed these deductions by nume- 

 rous injections. On introducing a liquid into the circulatory system, 

 either by the heart or the lacunae, he has always injected the inter- 

 membranular space of the tracheae. — Comptes Rendus de V Acad^mie 

 des Sc. Jmy. 28, 1850. 



LONG-SUSPENDED VITALITY OF A SNAIL. 



To Richard Taylor, Esq. 



Sir, — Instances have frequently occurred proving the extraordinary 

 powers of vitality which some of the MoUusca possess. Several spe- 

 cies belonging to the family Helicidae have been known to remain 

 alive for upwards of two years in a torpid state, without the possessors 

 of the specimens having even been aware that the shells contained 

 living inhabitants. An extraordinary instance of this power possessed 

 by snails has recently occurred here, which may prove interesting to 

 many of your readers. In March 1846 a series of shells was pre- 

 sented to the British Museum by Charles Lamb., Esq., collected by 

 him some time previously in Egypt, Greece, &c. Amongst these 

 were two specimens from Egypt of the Helix maculosa *, Ferussac, 

 " the Snail of the Desert," as it is generally called, and which is found 

 in great abundance living in the dry and arid deserts of Egypt and 

 Syria. On the 25 th of March 1846 the two specimens were fixed 

 upon tablets and placed in the collection amongst the other moUusca 

 of the Museum. There they remained summer and winter, fast fiixed, 

 gummed down upon the tablet, and immured in their prison till March 

 1850, four entire years after they had been first placed there, and 

 without the slightest suspicion having been awakened that one of 

 them contained a living inhabitant. How long they had been in the 

 possession of Mr. Lamb before he presented them to the Museum I 

 do not know. About the 15th of March 1850, having occasion to ex- 

 -amine some shells in the same case as that in which these two Helices 

 were contained, 1 observed that in one of them a thin glassy-looking 



* Helix maculosa, Von Bom, Ferussac, Hist. Nat. MoU. Terr, et Fluv. 

 t.28. f. 9-10. 



