August 28, 1914] 



SCIENCE 



305 



had been previously denied by Creplin^" and 

 von Seihold.''-'^ 



Leidy, in his monograph on the Gregarina, 

 published this year, attributes the failure on 

 the part of these investigators to note the pres- 

 ence of muscular strise, to the inferiority of 

 the microscopes used on the continent of 

 Europe compared vfiih those in use in England 

 and America (1849). 



Finally in a third paper published February, 

 1850, Philadelphia Proc. Acad. Nat. Sci., 

 Leidy writes 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 reflect- 

 ing upon the essential conditions of life. 

 Four months since he exhibited to the Acad- 

 emy numerous drawings and specimens of 

 Entophyta 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 ani- 

 mals, and less frequently upon the interior, 

 most usually upon diseased surfaces, but the 

 grov?th of such parasites had not been pointed 

 out as a normal and common condition as in 

 the case of entozoa. 



He next reviewed the theory of generation. 

 He inclines to the opinion that sexual ele- 

 ments are absolutely necessary for the per- 

 petuation of germs. He considered the alter- 

 nation of generation in certain animals no 

 objection to the law, for after successive devel- 

 opments an admixture of sexual elements is 

 observed to be necessary. The reproduction 

 among Cryptogamia may probably often ex- 

 hibit phenomena analogous to the alternation 

 of generation of animals, but universally he 

 thinks it will be discovered that a true sexual 



10 Wiegmimn's Archiv, 1846, 1 Band, S. 157. 



11 Wiegm-ann's Archiv, 1838, 2 Band, S. 308. 



mixture 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. Leidy thinks that sexual 

 admixture would be discovered to take place in 

 the mycelium. In numerous instances it had 

 been observed among the Algse. He stated he 

 thought he had noticed the process in Achyla 

 prolifera, and gave a description of the phe- 

 nomena. 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 draw- 

 ings of new entophyta observed growing in the 

 ventriculus of Passalus cornutus, a remarkable 

 one growing in a honey-like liquid in the pro- 

 ventriculus of the larva of Arctia Isabella, 

 another from Acheta ahhreviata, etc. He re- 

 marked that when such plants were found in 

 animals they were usually very abundant. 



Dr. Leidy then stated that very slight modi- 

 fications in the five essential conditions of 

 life were sufficient to produce the vast variety 

 of living icings upon the globe. As an in- 

 stance, he mentioned he had lying upon his 

 table a saucer with a cork bottom, in which 

 lay a partially dissected Passalus cornutus half 

 immersed in water. Two days afterwards he 

 noticed on the part of the insect above the 

 water a quantity of Mucor mucedo growing, 

 and from the part within the water numerous 

 fine, stiff filaments, which upon examination 

 proved to be Achyla prolifera; upon the cork 

 around the insect grew a third genus, con- 

 sisting 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 that he had had the good 

 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. 



