CH. VIII] 



MUCOR. 



115 



the coalescence of two similar protoplasts 1 . When this is 

 the case the process is known as conjugation, but it must 

 be recognised that it is essentially a sexual process. 



~ff. 



FIG. 50. 



CONJUGATION OF MUCOR. 

 a, b, c, d, e, f, g, represent successive stages ; 

 h, fully formed zygospore. 



The first thing that can be seen is the approximation 

 of two branches of the mycelium which are richly pro- 

 vided with protoplasm, and which finally meet by their 

 swollen ends (see fig. 50). The next stage consists in the 

 formation of a cross wall in each branch, and finally the 

 collections of protoplasm thus isolated are allowed to meet 

 by the degeneration of the ends of the branches. There 

 is thus formed a central cell containing the united 

 contributions from the conjugating mycelial branches. 

 This cell is known as the zygospore ; it is characterised by 

 a rough, dark-coloured outer coat, and it remains attached 

 to the now empty mycelial branches, which are sometimes 



1 Protoplast means the protoplasmic contents of a single cell. 



82 



