THE FERTILIZATION OF AMGEBA PROTEUS. 2 27 



stage on. In his paper on the Encystment of Amoeba proteus 1 

 he describes compound cysts which I would interpret as a late 

 stage (with protecting gelatinous membranes), of the stage shown 

 in my Fig. 12 of the original paper (section shown in Figs. 13, 14 

 of present paper). Each one of his cysts I would interpret as 

 one of the sporoblasts (Fig. 14), which, by independent growth, 

 reaches the size he describes (about 80 microns). The periphe- 

 ral granules (Fig. 14, b) of my sporoblasts become his nuclei of 

 the cyst and later, the nuclei of the minute amoebae with stellate 

 pseudopodia (Amoeba radiosd). 



In conclusion I would substitute for the -tentative life-cycle 

 published three years ago, the following : The ordinary Amoeba 

 protetis reproduces asexually by division (seen in every laboratory); 

 ultimately the asexual cycle is replaced by the sexual, the condi- 

 tions of which, periods, etc., are entirely unknown; the sexual cycle 

 is inaugurated by the multiplication through division of the nu- 

 clei until many "primary" nuclei are formed; these primary 

 nuclei fragment directly into minute granular nuclei correspond- 

 ing to the "secondary" nuclei of Polystomella, Centropyxis, etc. 

 In Amoeba the secondary nuclei may be called the "gametic" 

 nuclei ; the gametic nuclei fuse to form fertilization nuclei ; in 

 these the fused karyosomes fragment to form finely divided chro- 

 matin (it is, strictly speaking, not a chromidium for it is entirely 

 intra-nuclear), while a vacuole forms in the interior; this vacu- 

 olated fertilization nucleus becomes a center of multiplication 

 (equivalent in every way to a sporozoon sporoblast) ; by accu- 

 mulation of these fine chromatin granules the peripheral or " ter- 

 tiary " nuclei are formed ; the tertiary nuclei, surrounded by a 

 minute bit of plasm, grow into the pseudopodiospores observed 

 by Scheel (hypothetical) ; these young pseudopodiospores break 

 away from the parent cyst and develop into young amoebse for- 

 merly known as Amoeba radiosa, and these, in turn, develop into 

 the ordinary Amoeba proteus of pond and laboratory. 



Columbia University, 



New York City, August 10, 1907. 



1 Festschrift fiir Carl von Kupffer, Jena, 1899. 



