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reached the organism tends to reproduce itself. In Protista, as 

 described in the last chapter, two principal types of reproduction 

 occur namely, simple or multiple fission. In either case the 

 organism grows to its full specific size, and then divides into smaller 

 individuals ; the greater the number of daughter-individuals pro- 

 duced at each act of reproduction, the more minute those daughter- 

 individuals. Following the act of reproduction comes a period 

 of growth, during which the small forms grow up into full-sized 

 individuals which reproduce themselves in their turn. 



Thus the life-history of a Protist may be described as an alterna- 

 tion of periods of growth and periods of reproduction. If, how- 

 ever, the life-history consists of only these two events in alternating 

 succession, it is an infinite series, not a cycle ; continuous, not 

 recurrent. Possibly such a condition, varied only by states of 

 repose interrupting the vital activity of the organism is found in 

 Bacteria and allied forms of life, where true syngamy apparently 

 does not occur. But it is probable that in all Protozoa, as in all 

 Metazoa and plants, the life-history is a recurrent cycle, of which 

 an act of syngamy may be taken as the starting-point ; this point 

 will now be discussed. 



2. The Occurrence, of Syngamy in the Series of Living Beings. 

 With regard to this question, there are two possibilities ; first, that 

 syngamy and sexuality constitute a fundamental vital phenomenon, 

 common to all living things ; secondly, that it is an acquisition at 

 some period or stage in the evolution of organisms, and not a 

 primary characteristic of living beings. The sex-philosopher 

 Weininger* has argued in favour of the first of these hypotheses, 

 and goes so far as to regard all protoplasm as consisting primarily 

 either of arrhenoplasm '(male) or thelyplasm (female), standing in 

 fundamental antithesis to one another, and combined in varying 

 proportions in a given cell or sample of the living substance. A 

 view essentially similar has been put forward by Schaudinn, and 

 is discussed below. 



It is beyond question that sexuality is a universal attribute of 

 all living beings above the rank of the Protista, whether animals 

 or plants. In Protista, however, syngamy has not been observed 

 to occur with certainty in the Bacteria and organisms of a similar 

 type of organization. It is true that certain rearrangements of 

 the chromatin, observed in some larger organisms of the bacterial 

 type at certain phases of their life-history, have been compared to 

 sexual processes, but such an interpretation is, to say the least, 

 highly doubtful. In Protozoa, syngamy. has been observed to 

 occur in a vast number of forms, but by no means in all. In the 



* Weininger, 0., " Sex arid Character," chapter ii. London : W. Heinemann, 

 1906. 



