SPECIAL MORPHOLOGY OF THE PROTOZOAN NUCLEUS 



26l 



The micronuclei of Infusoria were first observed in division by Bal- 

 biani ('58, '59), but were incorrectly interpreted as bundles of sperma- 

 tozoa, an error which Biitschli ('76) was the first to point out. 

 Biitschli showed that these supposed bundles are nothing more than 

 the micronucleus in division, and he correctly interpreted the micro- 

 nucleus as analogous to the nuclei of tissue-cells. In the figures 

 which were made at this time, there is a distinction between chro- 

 matin and achromatin {e.g. Paramecium), and a mass of "achro- 

 matic" substance is pictured at each pole (cf. Fig. 138, b). Subsequent 





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Fig. 137. — Division in Ammba ciystalligera Schaud. [SCHAUDINN.] 

 s, division-centre. 



observers have obtained similar results. Maupas ('89) showed that 

 the spindle figure is made up of two distinct parts, and Hertwig ('89, 

 '95) made out the granular character of the chromatin, and in his 

 later work ('95) showed that the resting nucleus as well as the divid- 

 ing nucleus has an achromatic body. The relation of the intra- 

 nuclear body in the resting nucleus and in dividing forms was not 

 made out, although Hertwig assumed that the spindle in the latter is 

 derived from the division-centre. The later stages of the dividing 

 nucleus show the chromatin massed at the two ends in front of a 

 cap (pole-plate) of achromatic material, while a strand similar to that 

 in Euglena, connects the two ends (Fig. 139, D—H). 



It was Hertwig ('77), also, who gave the first account of the origin 

 of the achromatic spindle-figure in the division of the macronucleus 

 of the peritrichous ciliate Spirochona gemmipara. In this nucleus 



