404 Scientific Intelligence. — Zoology. 



have satisfied us that it would form a very valuable reagent ; 

 for it passes very readily to red under the action of acids, and 

 returns to blue under that of alkalies. With the oxalate of am- 

 monia, it gives a precipitate of a deep blue colour, and with ni- 

 trate of silver a very pleasant greyish-blue colour, which fur- 

 nishes a very good colour for drawing. 



25. Microscopical Observations on Fresfi- Water Mussels. — 

 M. Raspail read to the Academie des Sciences, on the 14th 

 July 1828, a letter, in which he detailed the results obtained 

 by him from new microscopical observations made on fresh-wa- 

 ter mussels. " Having placed," says the author, " on the 1st 

 July, two fresh- water mussels in a glass jar, I observed that the 

 excrementitial extremity expelled at certain intervals a small 

 parcel of a yellowish-white colour, and about half a centimetre 

 long. This granular parcel, when torn asunder on the object- 

 bearer, gave out a number of small bivalves, which opened and 

 shut their shells in a lively manner. Each of the valves was of 

 a triangular form, the hinge forming the hypothenuse. When 

 open, they were one-third of a millimetre in length, and one- 

 sixth when closed. This triangular form disappeared when the 

 two valves ceased to be parallel to the object-bearer; the animal 

 was scarcely distinguishable from the granulations of the shell. 

 In another parcel, I found bivalves furnished with an umbilical 

 cord, the commencement of which proceeded from one of the 

 notches formed by the commissure of the two valves."" Lastly, 

 when these bivalves were placed on the edges of their shell, it 

 was easy to distinguish, on the umbo of each valve, an apex, 

 turned inwards, nearly at a right angle, formed by a rib, si- 

 milar to that which in this position surrounds each valve like 

 a rim. But this apex was accompanied on each side by a mem- 

 branous prolongation, which was attached to the edges of the 

 valves. M. Raspail mentioned the experiments which led him 

 to conclude that the apex of the young shells observed by him 

 is at that period formed solely of phosphate of lime, and that 

 there is scarcely any carbonate in it His new observations con- 

 firm, 1^/, What M. Jacobson has said respecting the two um- 

 bones, which that author, however, has not, in his opinion, de- 

 scribed with accuracy ; and, 2d, The existence of the umbilical 

 cord described by Koelreuter. But these observations invalidate 



