FERTILIZATION BY AUTOGAMY 



139 



In this lowest group of animal forms we find every grade in com- 

 plexity in the sequence of syngamic processes, from those of undoubt- 

 edly primitive character to processes quite as complicated as in many 

 metazoa. We may pass from cases where only the one cell is involved, 

 fertilization taking place by union of two chromatin masses derived 

 from the same primary nucleus (autogamy) ; through cases where the 

 chromatin has had the same ancestry but is derived from different 

 cells (endogamy); to cases where sex differentiation and maturation 

 processes are quite as complicated as in higher animals and plants 

 (exogamy). With our present incomplete knowledge of the life his- 

 tory of lower forms, no great value is to be attached to such a classi- 

 fication, but its main purpose is served in providing a convenient 

 frame for attaching the manifold variations presented by the phe- 

 nomena of syngamy in protozoa. 



A. FERTILIZATION BY AUTOGAMY (AUTOMYXIS, HARTMANN). 



In the primitive forms of protozoa, as in those of plants, this method 

 of fertilization is widespread, and whatever may be the significance, 

 its wide distribution among the most diverse of these lower forms and 

 under the most varied conditions of life, indicates a natural and simple, 

 if not primitive, fertilization phenomenon. Even in these more primi- 

 tive cases, however, grades in complexity of the processes involved 

 are to be observed, and the transition from autogamy to endogamy 



FIG. 50 



. '*.', 



Ameba Umax budding, division, and idiochromidia forming stages. 



may occur in the same group. So far as the protozoa are concerned, 

 the most primitive methods are to be found among the free and 

 parasitic amebse, but even here there are indications of a more 

 advanced process. 



The main element that enters into the complexity of these more 

 primitive cases of autogamy is the formation of so-called secondary 

 nuclei from idiochromidia and the differentiation of somatic and 



