1850.] 7 



the Entomostraca, and includes 18 new genera and the names of 183 new species, 

 to be published in the volumes of the Exploring expedition. The continuation, 

 Am. J. Sci. 8,424 428, is devoted to the Isopoda and contains five new genera 

 and characters of eleven new species. 



20. L. R. GiBBEs. Tuomey's Report on the Geology of South Carolina, 

 Columbia, 1848 (distributed in 1849) contains a "Catalogue of the Fauna of South 

 Carolina " in which there is an excellent catalogue of the Crustacea by Prof. 

 Gibbes of Charleston. 



A paper was read from I\Ir. Conrad, describing new species of fresh 

 water shells from Arkansas and from Australia, and referred to a com- 

 mittee, consisting of Mr. Phillips, Dr. Wilson and Dr. Griffith. 



Dr. Leidy offered the following remarks: 



Dr. Leidy stated it was now eighteen months since he had sought for Entophyta 

 within living animals, having been previously impressed with the belief of their 

 existence upon reflecting upon the essential conditions of life. Four months 

 since he exhibited to the Academy numerous drawings, and specimens of ento- 

 phyta obtained from living animals ; he now exhibited others. 



The essential conditions of Life are five in number, viz., a germ, nutritive 

 matter, air, water, and heat. The four latter undoubtedly exist in the interior of 

 living animals, animal or entozoa germs also are well known to exist, and it was 

 rendered extremely probable that vegetable germs would also exist, and with 

 them all the conditions necessary to vegetable growth. Plants have been very 

 frequently observed growing upon the exterior of animals and less frequently 

 upon the interior, most usually upon diseased surfaces, but the growth of such 

 parasites had not been pointed out as a normal and common condition as in the 

 case of entozoa. 



Dr. L. next reviewed the theory of generation. He inclines to the opinion 

 that sexual elements are absolutely necessary for the perpetuation of germs. He 

 considers the alternation of generation in certain animals no objection to the law, 

 for after successive developments an admixture of the sexual elements is observed 

 to be necessary. The reproduction among Cryptogamia may probably often exhibit 

 phenomena analogous to the alternation of generation of animals, but universally 

 he thinks it will be discovered that a true sexual admixture takes place in every 

 species of these plants at some period of their life. According to the observations 

 of Schimper it is necessary among the mosses. From an observation made by 

 Klencke, upon a fungus which grew upon a diseased surface. Dr. L. thinks that 

 sexual admixture would be discovered to take place in the mycelium. In nume- 

 rous instances it had been observed among the Algae. He stated he thought he 

 had noticed the process in Achyla prolifera, and gave a description of the pheno- 

 mena. He finally considers that science is on the eve of demonstrating the 

 existence of a law "that an admixture of sexual elements is necessary for the 

 perpetuation of specific life germs." 



He then exhibited numerous elaborate drawings of new entophyta observed 

 growing in the ventriculus of Passalus cornutus, a remarkable one growing in a 

 honey-like liquid in the proventriculus of the larva of Arctia Isabella, another 



