178 



membranous capsule, each of which produces from 3 to 8 young, 

 which, on escaping from the egg, are of various sizes, and very 

 active. 



But the most singular part of the history of these animals is, that 

 they not only perpetuate their species as above described, but also 

 by a natural division of their body into two portions, the head part 

 reproducing a tail, and the tail a head in about fourteen days. These 

 appearances are represented in annexed drawings, and several expe- 

 riments are detailed in further illustration of their reproduction, 

 showing that a perfect animal is producible. 



Some Experiments and Researches on the Saline Contents of Sea- 

 water, undertaken with a view to correct and improve its Chemical 

 Analysis. By Alexander Marcet, M.D. F.R.S. Honorary Pro- 

 fessor of Chemistry at Geneva. Read June 27, 1822. [Phil. Trans. 

 1822, p. 448.] 



At the commencement of this paper Dr. Marcet, after adverting 

 to the conclusions at which he arrived in some former researches 

 communicated to this Society, notices the extraordinary assertions 

 of Rouelle and of Proust respecting the existence of mercury in sea 

 water. By a very careful examination, however, of bay salt, he was 

 unable to detect the smallest trace of that metal ; nor did he find it 

 in a sample of Sel de Gabelle obtained from Calais for the purpose 

 of examination. 



Dr. Marcet next examined sea water, with a view of ascertaining 

 whether any nitrates are present in it : with this view he added sul- 

 phuric acid and gold leaf to the concentrated bittern, and boiled the 

 mixture, but the metal was not in the least acted on ; when, how- 

 ever, the smallest quantity of nitre was added, the gold was instantly 

 dissolved. Hence the absence of nitric salts in sea water may be 

 inferred. 



In examining some of the same bittern for earthy and metallic 

 salts, the author found that neither alkalies nor their carbonates 

 throw down anything but magnesia, and that no muriate of lime 

 appears in any case to be present. Selenite and carbonate of lime 

 were, however, found in the matters deposited during the first eva- 

 poration of the transparent and pure sea water. 



When sea water is evaporated to dryness, and the residue sub- 

 mitted to distillation at a red heat, Dr. Marcet found that a portion 

 of sal-ammoniac sublimed. Lastly, he observes, that no sulphate of 

 soda is discoverable in sea water, but that it affords, on evaporation 

 along with other salts, certain rhombic crystals, which are triple 

 sulphate of potash and magnesia. 



