319 



Dr. C. T. Jackson explained a specimen from a vein of 

 Iron Ore, on the banks of the Alleghany River, in Penn- 

 sylvania, presented to the Society by J. W. Hall, Esq. 



It was an argillaceous carbonate of iron, which had assumed 

 pseudomorphous crystalline forms, which, with the cracks pro- 

 duced by desiccation, gave it very much the appearance of a fos- 

 sil jaw and teeth. It probably contained about thirty per cent, 

 of iron. 



Dr. Burnett made some remarks on Naviculce. 



About these, the opinion of naturalists has been frequently 

 changed ; they have sometimes been considered as plants, at 

 others as animals. Having recently carefully studied the Navi- 

 cuIcB with a powerful Spencer Microscope, he said that they were 

 unquestionably animals. In judging of the animal or vegetable 

 nature of the Infusoria, many points once supposed distinctive 

 are now known to be common to both animals and vegetables. 

 For instance, adaptive motion is not proof that the object is an 

 animal ; it has been recognized in plants known to be such by 

 chemical composition ; neither is the mode of reproduction dis- 

 tinctive. The point is principally to be decided by their ana- 

 tomical structure. The siliceous shells of Naviculce, though 

 having some marking of vegetable cells, yet possess certain 

 strise and marks which are not vegetable. His specimens were 

 obtained from the internal surface of intestinal worms found in 

 the rock cod ; they were g^^ of an inch in length, and 2^\p^ of 

 an inch in width. These animals have been divided into two 

 classes, the ribbed and the ribless ; his specimens were of the 

 latter class. He was able to trace an opening at the top, or a 

 mouth, like the sucker of a leech, by which they were found 

 hanging to the internal surface of the intestinal worms; he 

 could also trace an oesophagus, stomach, and anus. He is sus- 

 tained in his opinion by the structure of Planar ice. Whatever 

 may be said of other Naviculce, we may justly consider this 

 species an animal parasite. 



Dr. C. T. Jackson inquired if any animals secreted siliceous 

 matters ; he supposed this to be characteristic of vegetables. 



