CHYTRIDIINEAE 59 



The nature of chromidia or collections of extranuclear 

 chromatin is discussed in Chapters I and TV. 



Encysted Euglenae alone are attacked by Polyphagus, 

 the rhizoids of which may attach as many as fifty. From 

 the end of the rhizoid a branched haustorium pervades and 

 soon exhausts the prey. The protoplasm is dense and 

 contains many oil drops. The nucleus and chromidium 

 pass with the protoplasm into the sporangial diverticulum. 



The chromatin of the resting nuclei is massed at one side 

 of the nucleus, Fig. 14, C. In mitosis the greater part of 

 this chromatin lies around the spindle, in optical section 

 showing as a dark crescent on each side at some distance 

 from the spindle, Fig. 14, C 1 . 



The zygote is formed from two ordinary vegetative 

 cells ; the male puts out a long slender rhizoid on which a 

 swelling arises at the point where it comes in contact with 

 the female gamete, Fig. 14, D. The male nucleus enters 

 the swelling first, and, after a series of changes in which the 

 nuclei are reduced in size, the two chromidia fuse into one 

 mass at the sides of which the two nuclei are embedded. 

 Fusion of the nuclei appears to occur only after germination 

 has begun. Nuclear divisions take place only in sporangia. 

 The chromosomes number 10 or 12 and are very small. 

 The spindle is internal. The chromatin which surrounds 

 the spindle is used in part as nutritive material in the growth 

 of the sporangium. The chromidium surrounds both nucleus 

 and oil-drop in the zoospore of Polyphagus, Fig. 14, A. 



