FORMATION OF GAMETES— AUTOGAMY 85 



place by the extrusion of one or more reduction bodies. In the case of 

 the microgametocyte, nuclear multiplication takes place till numbers of 

 nuclei are formed (Fig. 337). These nuclei at first appear as minute 

 aggregations of chromatin granules. They change their form on the 

 surface of the cytoplasm till they appear as dense comma-shaped struc- 

 tures. Each is then separated with a small amount of cytoplasm, which 

 contributes to the formation of flagella. In the blood parasites belonging 

 to the genera Plasmodium, Hcemojjroteiis, and Leucocytozoon, the macro- 

 gametocyte produces a single macrogamete, as in the coccidia, by the 

 rapid extrusion of reduction bodies. The microgametocyte gives rise 

 in the course of a few minutes to six or ten microgametes by a violent 

 process known as exflageUation, which occurs normally in the stomach of 

 the invertebrate host, but which may be observed in an ordinary moist 

 preparation of blood under the microscope (Fig. 381). The details of the 

 process will be described below in the section devoted to these parasites, 

 but it may be noted here that the function of the reduction bodies referred 

 to above is far from clear, and the assumption that the process is com- 

 parable with the formation of polar bodies during maturation of the 

 ovum of higher animals does not appear to be correct. 



AUTOGAMY. — A process of syngamy which may be defined as self- 

 fertilization has been described for certain Protozoa under the name of 

 autogamy. In its most complete form the nucleus of a single individual 

 divides to form two daughter nuclei. Each of these undergoes reduc- 

 tion divisions, after which the two surviving nuclei unite. In the 

 case of Entamoeba coli, Schaudinn (1903) described autogamy in the 

 encysted stages. The single nucleus of the encysted form divides to give 

 rise to two nuclei. Each of these gives off two reduction bodies, after 

 which they divide to form four nuclei, wliich are arranged in pairs at 

 opposite sides of the cyst. One of each pair is a stationary nucleus and 

 one a migratory nucleus. The migratory nuclei move to opposite sides 

 of the cyst, where they unite with the stationary nuclei. The cyst again 

 has two nuclei, which proceed to divide till the characteristic eight nuclear 

 stage is reached. The writer (1907) saw certain stages in the development 

 of the cysts of Entamoeba miiris, which appeared to supply a confirmation ' 

 of Schaudinn's account of E. coli, but there is little doubt that the appear- 

 ances were capable of another interpretation. All evidence goes to 

 show that no such process actually occurs in the cysts of E. coli or any 

 other anio-ba. A somewhat similar process was described by Prowazek 

 (1904f/) in the cysts of Prowazekella laceyta', while Schilling (1910) recorded 

 its occurrence in Trypanosofna lewisi. It seems perfectly clear that in 

 none of these cases was there sufficient evidence to justify the conclusions 

 whicli were made. 



