OF ARTS AND SCIENCES. 179 



omists would, previously to immersing the animal in spirits, inject the 

 abdominal aorta with size or gelatine, colored by vermilion. 



" There is only one expression in Dr. Meigs's memoir in which I am 

 not disposed to acquiesce, where he says ' it is not to be believed that 

 a breathing, &c., mammifer can be developed independently of a 

 placenta' (p. 329). I have met with so many unexpected exceptions 

 to assumed general rules in the animal economy, so many proofs that 

 the Creator operates by ways diversified infinitely beyond human cal- 

 culation, as to adopt no scientific dogma whilst any means of testing 

 it by observation remain untried. It would be most desirable that the 

 female opossum should be sought for at the period shown by Dr. Meigs 

 to be that when she would be most likely to have embryos in the 

 uterus, and the nature of the connection between the mother and off- 

 spring be examined. A placenta may be defined as a vascular, vil- 

 lous, or cellular process from the outer surface of the chorion, inter- 

 lacing with a similar process from the inner surface of the womb, and 

 producing an adhesion of the chorion thereto difficult to be overcome, 

 and often not without laceration. The presence of such an organ, 

 simple or subdivided, would be easily determined in an opossum killed 

 towards the latter period of her brief pregnancy, say from March 1st to 

 7th. The analogy between the condition of the new-born young in 

 the kangaroo, in which no placenta is formed, and the opossum is so 

 close, that, if I were to allow myself to anticipate what unbiased ob- 

 servation ought to decide, I should expect as close an analogy in the 

 condition of the foetal membranes and appendages." 



Mr. Teschemacher exhibited some specimens of anthracite 

 coal, containing what he supposed to be fossil seeds, as he had 

 carefully decarbonized the internal substance of them, and by 

 the assistance of the Oberhausser microscope belonging to 

 Professor Agassiz, with a power of 700 diameters, had foimd it 

 to be a mass of distinct cells. Some of these seeds were sur- 

 rounded by impressions resembling spinous processes, \vhich 

 were uniform and symmetrical. He also stated, that lately 

 discovered specimens had confirmed him in his opinion, that 

 most of the appearances usually called slickensides in the an- 

 thracite coal were the external parts of large fossil plants ; also, 

 that the small, uniform striae frequent in the coal, and which 

 are sometimes found covering pieces of a conical form, are the 



