BASIDIOBOLUS. 



77 



wall cutting off a small cell at the end of the beak (Fig. 25, B). The 

 manner in which this wall is laid down is worthy of special notice 

 here, since it is formed as in the higher plants, namely, through the 

 instrumentality of the kinoplasmic connecting fibers, appearing at 

 first as a cell-plate. Apart from Chara this is the only instance 

 as yet known among the lower cryptogams in which a cell-plate is 

 thus formed. Immediately the nuclei have entered the beaks, and 

 prior to the prophase of the nuclear division just mentioned, and also 

 before an increase in size of the female gamete, a hole is formed in 

 the transverse wall separating the two gametes. 



The two daughter nuclei cut off in the ends of the beaks gradually 

 disappear, while the other two pass down deeper into the cytoplasm 



FIG. 25. Formation of gametes in Basidiobolus ranarum Eidam. (After Fairchild.) 



A, two gametes showing the beaks ; the nuclei, which are in the beaks, are in the resting condition ; 



the hole has already formed between the gametes. 



B, the nuclei have divided and two of the daughter nuclei are cut off in the ends of the beaks, while the 



other two, which have increased in size, have passed down near the opening in the transverse wall ; 

 the female gamete has increased greatly in size, the male retaining its former dimensions. 



of the cells (Fig. 25, B). The male nucleus now passes through this 

 opening and comes in contact with the female nucleus (Fig. 26, C) . 

 During these movements the nuclei attain their original size, and each 

 contains one or more interwoven nuclear threads, in which chromatin 

 granules are situated at rather long intervals. In this condition the 

 two nuclei remain some time before fusing. The entire cytoplasm 

 of the two gametes is utilized in the formation of the young zygospore, 

 which now forms about itself a very thin wall, within which the 

 thick endospore, consisting of several layers, is gradually developed. 

 Owing to the difficulty with which fixing fluids penetrate the thick 

 wall of the zygote the exact time of fusion of the male and female 

 nuclei is not easily determined, but as the zygospore approaches 

 maturity the fusion is complete, so that no trace of male and female 



