226 GARY N. CALKINS. 



plete division of the cell body. After this division, the daughter 

 nuclei fragment, forming a mass of minute chromidial granules 

 which are distributed throughout the cell. From the two masses 

 of granules thus formed secondary nuclei arise by fusion as in the 

 case of Centropyxis, Arcella, Polystomella, and rhizopods gener- 

 ally, and these two nuclei, after preliminary division giving rise to 

 what Schaudinn interprets as "polar body" equivalents, divide 

 for a third time, the products of this division fusing two by two. 

 The partly separated protoplasmic body then reunites and the 

 fertilization cell contains two fertilization nuclei. These two 

 nuclei then divide twice forming eight nuclei altogether and these 

 finally become the nuclei of eight amoeboid spores. 



Except for the maturation divisions, which future study 

 may reveal, the process of fertilization in Amoeba protens is thus 

 strikingly similar to that of Entamoeba coli the gametic nuclei 

 arising by fragmentation instead of by division as in the latter 

 case. The fertilization nucleus forms, not eight, but many 

 daughter nuclei, and from analogy, I would expect these vacuo- 

 lated centers of multiplication or sporoblasts in Amoeba proteus to 

 produce from 70 to 100 pseudopodiospores. 



The formation of the secondary nuclei in Amoeba proteus dif- 

 fers in some important respects from the process in other rhizo- 

 pods. In Arcella, Centropyxis and Polystomella for example, it 

 occurs in the chromatin substance that is either transfused through 

 the membrane of the nucleus or formed by fragmentation of the 

 nuclei. In all cases that have been worked out, however, the 

 secondary nuclei are formed from the substance of this chromid- 

 ium and we can thus trace their history back indirectly to the 

 primary nuclei. In Amoeba proteus on the other hand, the nuclei 

 are not formed from diffused chromatin nor from the fragments 

 of primary nuclei but they form directly within the primary nuclei 

 and emerge from it as fully formed secondary nuclei. In this 

 case, as in the other cases, the secondary nuclei are the gametic 

 nuclei, only here their union is, so to speak, precocious and with- 

 out the customary gamete formation, while the union and 

 especially the further development within the parent cell, are un- 

 usual and unexpected discoveries. 



Scheel takes up the life history of Amoeba proteus from this 



