GEMMATION 71 



unequal in size that the process is regarded as one of budding or gemmation, 

 the nucleus of the bud arises by equal division of the nucleus of the parent, 

 so that the large and small daughter forms have their nuclei of equal size. 

 A method of formation of the nuclei of buds from chromidia has been 

 described as occurring in certain Protozoa. Thus, in the case of Entamoeba 

 histolytica, Schaudinn (1903) supposed that granules of chromatin occurred 

 in the cytoplasm outside the nucleus. These granules were supposed to 

 collect in groups at the surface of the organism, become organized into 

 nuclei, and enter the buds which were forming. Such a process certainly 

 does not occur in E. histolytica. Another instance in which nuclei have 

 been described as arising in this manner is that of Arcella vulgaris re- 

 ferred to above (Fig. 2). 



SYNGAMY AMONGST THE PROTOZOA. 



As m the higher animals and plants, at certain phases of development, 

 two cells unite and their nuclei fuse, so amongst the Protozoa a similar 

 process may occur. This is generally known as a sexual process, or 

 syngamy. It may take place in one of two ways: either two individuals, 

 which are known as gatnetes, unite by fusion of their cytoplasm, followed 

 by union, or haryogamy, of their nuclei; or two individuals become incom- 

 pletely united, and part of the nucleus of each passes over into the other 

 individual to unite with its nucleus. After this transference of nuclear 

 material the individuals separate. The process in which two individuals 

 unite completely is known as copulation, while that in which interchange 

 of nuclear material between two temporarily associated individuals takes 

 place is called conjugation. The two processes are not essentially different 

 from one another, for it may be considered that in conjugation each of 

 the two associated individuals really produces two gametes, one of which 

 is large and contains all the cytoplasm and a nucleus, while the other is 

 small and consists of a nucleus only. The small gamete produced by one 

 individual unites with the large gamete produced by the other. It is, 

 however, convenient to distinguish the process of copulation from that of 

 conjugation, as the latter is the characteristic method of syngamy amongst 

 the Euciliata. 



COPULATION. — This process consists in the union of two cells with 

 fusion of their nuclei. The cells are known as gametes, while the single 

 uninucleated cell resulting from the union is called a zygote, and the nucleus 

 of the zygote, which is the product of the union of two gamete nuclei, is 

 the synkarion. The uniting gametes may be the ordinary individuals 

 which have ceased multiplying, or an ordinary individual, by a special 

 process of multiplication, may give rise to a number of smaller gametes 



