118 Dr Grant on the Structure and Nature of Flustrce. 



and without relenting the motions of the ciliae on their surface. About this 

 time from their fixing, the ciliae cease to move, and disappear, first at a parti- 

 cular part of the surface, and in the space of twenty- four hours longer they 

 cease their motions over the whole surface of the ova. In about two days af- 

 ter the ciliae have ceased to move, the ovum appears more swelled, the sur- 

 rounding margin becomes more transparent and colourless, and the yellow 

 matter, which appeared to compose the whole ovum, is now confined to the 

 central part. As the ovum enlarges and loses its bright yellow colour, it as- 

 sumes a form more nearly resembling that of a cell, and acquires a light grey 

 or whitish colour, with increased transparency in every part, excepting the 

 yellow central spot, which gradually diminishes in size. A delicate white 

 opaque line makes its appearance near the outer margin of the transparent 

 ovum, and passing round its whole circumference; this white line has the form 

 and nearly the size of a full-grown cell, and is the rudiment of the lateral cal- 

 careous wall of the cell. Towards the base of this rudimentary cell, we per- 

 ceive the gelatinous interior become more consistent and opaque at a particu- 

 lar point; from this dull spot within the cell we soon perceive short straight 

 tentacula begin to bud out, extending upwards in the direction of the future 

 aperture. The gelatinous spot from which the tentacula originated, assumes 

 the vermiform appearance of the body of a polypus, and we distinctly perceive 

 the bundles of fibres which connect its head with the base of the cell. The 

 aperture of the cell, in form of a crescentic valve, is perceptible before the in- 

 fant polypus extends so high in the cell, and is not a mere perforation made 

 by the polypus, as Lamouroux and some others have supposed. The struc- 

 ture of the polypus is perfected within a distinct shut capsule, and when we 

 first detect it protruding from the cell, it possesses all the parts of an adult 

 polypus, and vibrates the cilise of its tentacula with as much regularity and 

 velocity as at any future period. Before the polypus is capable of ])rotruding 

 from the aperture of the first cell, we perceive the upper part of that cell ex- 

 tending outward to form the rudiment of a second, in the same manner as we 

 observe at the tips of the branches in adult specimens, 

 ( To be concluded in next Number, \ 



Some Remarks an the Temperature and Climate of Shetland. 

 By William Scott, A. M., of the Royal Military College 

 at Sandhurst. — Communicated by the Author. 



xVt the request of Professor Jameson, I drew up a set of 

 Tables, exhibiting the temperature, wind, and weather, during 

 part of the years 1824 and 1825, as observed by myself at Bel- 

 mont, in the island of Unst, Shetland, in Long. 0° 51' West, 

 Lat. 60° 42' North, the thermometer being elevated QQ.^Z feet 

 above the level of the sea, and 300 yards distant from it. These 

 tables, however, prove too bulky for insertion in the Philoso- 



