394 



proportions in the masses, but the crystals may be a double salt, 

 composed of one equivalent of sulphate of soda, and one equiv- 

 alent of sulphate of magnesia; each retaining an equivalent of 

 water. In the masses, the closest approximation is 42 parts of 

 sulphate of magnesia found, instead of 46 parts required. 



The communication of Mr. Bishop embraces interesting facts. 

 These saline deserts cover extended areas, in different parts of 

 South America, and, so far as he has been able to learn, the 

 saline matter differs in kind at the different points. The ten- 

 dency of saline matter contained in any soil is to rise through 

 the aid of moisture to the surface, where, the water escaping, the 

 salt is deposited. This effect, contrary to the gravitating influ- 

 ence, is the most common cause of deserts, and may be exerted 

 everywhere, when the evaporation of water from a given surface 

 becomes much greater in amount than that surface receives in 

 the form of rain and dew. The cultivation of saline deserts by 

 washing down the saline matter, exhibits the opposite action of 

 water in restoring fertility, and it is by no means essential that 

 the water should contain organic matter to insure the full effect, 

 as the soil of deserts generally contains all the organic matter 

 of many years' accumulation. 



Dr. Wyman made a few remarks on some of the 

 habits of the painted tortoise (Emys picta) during the 

 breeding season, which he had recently observed. 



Dr. Wyman also gave some account of the develO|)- 

 ment of the dorsal cord in the Ale wive, (Alosa vernalis.) 



The dorsal cord has been generally described as terminating 

 anteriorly between the auditory capsules, and, in consequence, it 

 has been inferred that the true vertebral column does not extend 

 beyond the basilar portion of the occiput; and that the occiput 

 is the only part of the cranium which has a vertebral structure. 

 In the Alevvive, he had seen the dorsal cord, in the earlier 

 specimens, uniformly extending as far forwards as the space 

 between the eyes, and consequently into the region of the an- 

 terior spiienoid ; subsequently, as the face is enlarged, the anterior 

 part of the cranium seems to be carried forwards, and then the 



