8 [Feb. 



from Acheta abbreviata, etc. He remarked that when such plants were found in 

 animals they were usually very abundant. 



Dr. L. then stated that very slight modifications in the five essential conditions 

 of life were siiUlcient to produce the vast variety of living beings upon the globe. 

 As an instance, he mentioned he had lying upon his table a saucer with a cork 

 bottom, in which lay a partly dissected Passalus cornutus half immersed in water. 

 Two days afterwards he noticed upon the part of the insect above the water a 

 quantity of Mucor mucedo? growing, and from the part within the water nume- 

 rous fine, stiff filaments, which upon examination proved to be Achyla prolifera; 

 upon the cork around th'e insect grew a third genus, consisting of fine cottony 

 filaments, which were articulated, of which he exhibited a drawing; and upon 

 the insect at the surface of the water, but not within the latter, grew a fourth 

 genus, of which he also exhibited a drawing. 



He also stated he had had the jood fortune of observing in a single morning all 

 the stages of development of Achyla prolifera growing from some individuals of 

 Ascarides which had been lying in a dish of water for a few days. 



In reply to some remarks made by members. Dr. Leidysaid he could not admit 

 the doctrine of spontaneous generation, but rather thought modifications in the 

 essential conditions of life favorable to the development of different, and always 

 pre-existing germs derived from a parent. 



February 19th. 

 Dr. Morton, President, in the Chair. 



A letter was read from Mr. J.T. Becker, dated Paris, 10th December, 

 184-9, proposing exchanges with the Academy in Entomology. Referred 

 to the Committee on Entomology. 



Also a letter from H. Lecog, dated Clermon-ferrand, January 10, 

 18.50, proposing exchanges in Conchology with the Academy, or 

 with individual members of the Society. Referred to the Committee 

 on Conchology. 



Dr. Leidy offered the following observations : 



Dr. Leidy presented to the examination of the Society a colored and several 

 other drawings of what he termed an entophytic forest, taken from a portion of 

 the mucous membrane of the ventriculus of Passalus cornutus. He remarked 

 that at least six species of entophyta were found growing upon the mucous mem- 

 brane of the ventriculus of P. coinutus, which were often present in great quan- 

 tity, frequently some thousands, and which from their number, polymorphous 

 appearance of several species, and attachment to various appendages of the 

 mucous membrane, resembled very strikingly a miniature Brazilian forest, which 

 was heightened in some degree by the existence of a nematoid worm, which 

 recalled to mind the idea of one of the serpents of such a forest. 



A somewhat similar drawing he exhibited, taken from the small intestine of 

 Julus marginatus. 



Other drawings were also presented. Dr. L. stated that among his collection 

 of living Julides. he had a number of times observed individuals to become dull 



