24 



Native copper is also produced, in masses and in veins, both in 

 Nova Scotia and on Lake Superior; this metal being found in 

 large and regular veins in very great abundance in the Amygda- 

 loidal trap of Keweenaw Point, Ontanagon, and Isle Royale 

 districts, on Lake Superior. 



When trap rocks act upon slate rocks, they produce iron pyrites, 

 and occasionally silver ores, and with silurian limestones they 

 form lead and silver ores almost exclusively ; while, as before 

 stated, native copper generally results from their influence upon 

 the new red sandstone strata. Hence, the miner and the min- 

 eralogist are guided in their researches by a knowledge of these 

 geological laws, which seem to be universal in their application. 



Dr. D. F. Weinland gave an account of the Reproduction of 

 Parasitic Animals, and explained the phenomena of Alterna- 

 tion of Generation in the parasitic Trematoda of the Freshwater 

 Snails. The first generation of this animal exists, in the form of 

 " Distoma," in the intestines or lungs of Vertebrata, as a perfect 

 animal with genital organs producing eggs ; the next generation 

 exists as a yellow worm in the liver of the snails mentioned 

 above, with or without an intestine, their bodies being filled with 

 the third generation of the animal, viz : little worms with long 

 tails — the so-called Cercarians — which originate in the body of 

 the yellow worm by a kind of budding. In the third generation, 

 these Cercarians are brought forth by the mother, swim for a 

 while free in the water, and then become a kind of pupa ; form- 

 ing a cyst around themselves, and in this state seeming to wait 

 till, by chance, they are swallowed by a vertebrated animal in 

 which they become, in a few days, as is shown by experiment, a 

 perfect Distoma. 



Dr. Weinland had found a new species of Cercaria, the first 

 known in this country, in the liver of the Physa heterostropha, 

 and he concludes, from further investigations, that this Cercaria 

 belongs as a larva to a blackish-spotted Distoma, which he has 

 found frequently in the lungs of frogs and toads, and once in the 

 intestine of a turtle, and which he proposes to describe under the 

 name of Distoma atrlventre. 



He added that a similar alternation of generation takes place 

 in another order of Helminthes or Parasitic worms, viz : the 

 order of Cestoda. The investigations of Kuchenmeister and 



