14 THE PROTOZOA 



simple division, another and a sexual method of reproduction occurs. 

 His interpretation of the sexual organs of the Protozoa was given in 

 1858, when he maintained that the larger of the two kinds of nuclei 

 of Infusoria, the macronucleus, is the ovary, and the smaller one, or 

 micronucleus, the testis. He saw and pictured the striped appear- 

 ance of the micronucleus prior to division, and interpreted the stripes 

 as spermatozoa. The eggs were said to be formed in the macronu- 

 cleus, to be fertilized and then deposited on the outside, where they 

 develop into new ciliates. Stein at first opposed this assumption, but 

 in the second volume of his work on the Infusoria, misled by his 

 Acineta-theory, he practically adopted it, maintaining, however, that 

 the embryos develop in the nucleus first, and only later leave the 

 mother organism. Biitschli ('73) was apparently the first to point 

 out Balbiani's error, and in his epoch-making work of 1876, after 

 demonstrating the " striped " appearance of many egg-cells during 

 division (mitotic figure), he concluded that the stripings which Bal- 

 biani held to be spermatozoa were no other than this striated con- 

 dition of the nucleus during division. He held, therefore, that in 

 addition to the macronucleus there is a second and a smaller nucleus 

 in Infusoria, and to this he gave the name Nebenkern or micronucleus 

 ('76). Biitschli further showed at the same time that during conjuga- 

 tion the macronucleus or larger nucleus disintegrates, and that the 

 parts which Balbiani regarded as eggs are eliminated, to be replaced 

 by one of the subdivisions of the Nebenkern (micronucleus). His 

 interpretation of the process was equally happy. After observing 

 that a continued asexual division of certain forms resulted in decreased 

 size and a general " lowering of the life energy," he concluded that 

 the function of conjugation is to bring about a rejuvenescence ( Ver- 

 jungung) of the participants. He called attention to the similarity 

 between conjugation and fertilization of the egg in animals and plants, 

 and, at the same time, made the classic comparison between the body 

 of the metazoon and the chain of individuals which arise from one 

 individual protozoon subsequent to conjugation. 



In the same year Engelmann ('76) obtained very similar results. 

 Quite independently of Biitschli he also proved the error of Balbiani's 

 view, and came to a conclusion not far different from Biitschli's. 

 "The conjugation of the Infusoria," he said, "does not lead to repro- 

 duction through 'eggs,' 'embryonic spheres,' or any other kind of germ, 

 but to a peculiar developmental process of the conjugating individual, 

 which may be designated as reorganization." (Reorganization^ 



Neither observer noted the conditions which induce conjugation or 

 the mutual interchange of parts of the micronuclei, although both, 

 indeed, suspected that the latter might take place. The actual inter- 



1 Engelmann ('76), p. 628. 



