LIFE HISTORY OF AMCEBA PROTEUS LEIDY. 34! 



describe an apparently hitherto unknown method of reproduc- 

 tion; and third to record some observations upon the develop- 

 ment and growth of the forms produced by this new method. 



The first observer to suggest that another method of reproduc- 

 tion other than simple fission might obtain among the Amceba 

 was Varter ('56) who recorded the presence of numerous fine 

 granules which he observed filling the bodies of some Amceba 

 radiosa. These granules he looked upon as fragments of the 

 nucleus, and since, when they escaped from the body, they 

 moved with a curious jerky motion, he inferred that they must 

 be provided with flagella, and termed them spermatozoids. The 

 observations extended no farther. Again in 1863 he observed 

 the granulation of the nucleus in Amceba princeps, noting that 

 the original nucleus divided several times and gave rise to many 

 smaller nuclei, which he termed, though apparently with meager 

 foundation, reproductive cells. 



Wallich ('63) noted that when Amceba villosa "died," the 

 nucleus, which had divided several times, escaped from the body 

 surrounded by bits of protoplasm, of globular form. He observes 

 that the fate of these globules is unknown to him, but believing 

 that they might function in some reproductive process, termed 

 them scaroblasts. Referring to the many different species of 

 Amceba which appeared in his cultures, he writes (with reference 

 particularly to Amceba princeps, diffluens, and radiosa} : " It will, 

 I think, eventually be found that these are mere transitory 

 phases of one and the same species." Later, he observes with 

 greater conviction: "... though not prepared to affirm that 

 the whole of the varieties of Amcebce are reducible to a single, 

 primary, specific type, I candidly confess that the balance of the 

 evidence appears to me to point to such a conclusion, and to 

 indicate that the divergence in the form and outward characters 

 may be wholly dependent on the local and even temporary 

 conditions of the medium in which the young animal happens 

 to make its appearance in the world." 



It is to Scheel ('99) that we owe our first complete knowledge 

 of a type of reproduction different from the familiar method of 

 binary fission. In 1899 he described a process of reproduction 

 in Amceba proteus which he termed schizogony, after a somewhat 



