POLYTOMA 177 



couples, that there is a fusion of amoebulfe to form a Plas- 

 modium in Badhamia (though as the nuclei do not unite in 

 this case it cannot be called a true act of conjugation), and 

 that true conjugation has been recorded in Bodo. In all 

 these forms the conjugating individuals or gametes are either 

 perfectly similar, or, as in the case in Bodo saltans, differ 

 from one another only in a temporary change of habit. 

 But the case is not always thus : in some of the near allies 

 of Polytoma the gametes are very dissimilar, and we get a 

 forecast of the differentiation of sex which is so characteristic 

 both of the higher animals and plants. 



Polytoma uvella is colourless and devoid of chlorophyll, 

 but the majority of its nearest allies are green, having one or 

 more chromatophors containing chlorophyll. Their nutrition 

 is holyphytic, and they are so plant-like in structure and 

 in function that they are always described as plants in 

 botanical works. Yet the zoologist, recognising their affinities 

 to Flagellata, whose behaviour is clearly animal, cannot afford 

 to leave them out of consideration, and hence they are 

 classed in zoological works under the name Phytomastigoda, 

 or plant-like Flagellates. Some of them are of so much interest 

 and importance that they must engage our attention for a 

 while. 



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