324 University of California Publications in Zoology [Vol. 20 



The division of these amoebae differs from that of the parasitic 

 flagellates in that the centrosomes and intradesmose are found within 

 the nuclear membrane, the homologue of the latter structure, the 

 paradesmose, and the centrosome of the flagellates always being out- 

 side of the nuclear membrane, the relation of the centrosome to the 

 flagella in the flagellate making the extraniiclear pasition an essential 

 one for these structures in that group. 



In a recently published paper Yoshida (1920) describes a process 

 of autogamy in End-amoeba coli in which two, four, or even six, nuclei 

 may fuse to form a "syncaryon. " On the basis of his experiments, 

 he claims that "the daughter-nuclei in the cyst stage correspond 

 exactly to the gamete nuclei of other Protozoa," but gives no cyto- 

 logieal evidence of gamete formation. As a further step in the 

 process of autogamy he finds that the amoebae develop numerous 

 vacuoles and their nuclei shrink and degenerate until they finally 

 burst. The phenomenon he has described is one occurring occasionally 

 in parasitic amoebae when undergoing degeneration outside of their 

 normal host, and has no known relation to sexual or ordinary develop- 

 mental processes. The process of "autogamj-" was first described for 

 Endamoeba coli by Schaudinn (1903) and later figured by Hartmann 

 (1909) from descriptions in the earlier paper. Some of these figures 

 are similar to those showia on plate 29, of the one- and two-nucleate 

 amoebae with the large glycogen vacuole filling the center. However, 

 instead of adding the third stage, a four-nucleate amoeba, the first 

 stage, or a Blastocystis was again arbitrarily used as that resulting 

 from "autogamy" in the two-nucleate cyst. Along with these stages 

 Schaudinn added other phases of the yeast-like Bl-astocystis frequently 

 found in human faeces (Kofoid, 1921). This process has since been 

 figured in textbooks as the normal sexual process in amoebae. It has 

 been repeated in textbooks again and again for amoebae but thus far 

 no satisfactory cj-tological evidence has been brought forward to sup- 

 port such an interpretation for the ordinary steps in nuclear division 

 (pi. 29, figs. 1-7), or for the degeneration phases of amoebae that 

 have been placed in an alien environment. 



