3 6 ELEMENTARY BIOLOGY. [CHAP. 



swelling and eventual dissolution of the gelatinous interme- 

 diate matter. Sporangia, in which spores are produced by 

 division of the protaplasm, are commonly termed asci, and 

 the spores receive the name of ascospores. 



There appears to be no limit to the extent to which the 

 Mucor may be reproduced by this process of asexual deve- 

 lopment of spores, by the fission of the contents of the 

 sporangium; nor does any other mode of multiplication 

 become apparent, so long as the mould grows in a fluid 

 medium and is abundantly supplied with nourishment. 



But when growing in nature, in such matters as horse- 

 dung, a method of reproduction is set up which represents 

 the sexual process in its simplest form. Adjacent hyphae, 

 or parts of the same hypha, give off short branches, which 

 become dilated at their free ends, and approach one ano- 

 ther, until these ends are applied together. The proto- 

 plasm in each of the dilated ends becomes separated by a 

 septum from that of the rest of the branch; the two cells 

 thus formed open into one another by their applied faces, 

 and their protoplasmic contents becoming mixed together, 

 form one spheroidal mass, to the shape of which the coa- 

 lesced cell-membranes adapt themselves. This process of 

 conjugation evidently represents that of sexual impregnation 

 among higher organisms, but as there is no morphological 

 difference between the modified hyphae which enter into 

 relation with one another, it is impossible to say which 

 represents the male, and which the female, element. The 

 product of conjugation is termed a zygospore. Its cellulose 

 coat becomes separated into an outer layer of a dark black- 

 ish hue, the exosporium, and an inner colourless layer, the 

 endosporium. The outer coat is raised into irregular eleva- 

 tions, to which corresponding elevations of the inner coat 

 correspond. 



