MALE GERM-CELLS. 



137 



The mode of origin of the mother-cells differs considerably in different 

 ferns, but in all cases is essentially as follows : An ordinary cell on the 

 lower side of the prothallium swells and forms a hemispherical or dome- 

 shaped projection, which is soon separated by a partition from the original 

 cell (Fig. 72). Further divisions then follow in the dome-shaped cell such 

 that a central cell is left, surrounded by a 

 layer of peripheral cells (Fig. 73). By re- 

 peated divisions the central cell splits up 

 into the spermatozoid mother-cells (Fig. 71). 



Within each mother-cell the proto- 

 plasm arranges itself in a peculiar 

 spiral body, the sjyermatozoid^ which 

 is the male germ^cell. 



When the mature antheridium is 

 moistened, the peripheral cells swell 

 and thus press out the mother-cells 

 and spermatozoids (Fig. 74). The 

 latter escape from the mother-cells and swim about very actively 

 in the water. They appear as naked single cells, of a peculiar 

 corkscrew shape, and bear upon the finer spirals numerous ex- 

 tremely active cilia (p. 31), by 

 which they are driven swiftly 

 through the water. 



The Archegonia^ or female 



Fio. 73. (After Hofmeister.) — 

 Later stage in the development 

 of an antheridium of Pterix ser- 

 riilata. p, peripheral cell; c, 

 central cell from which the 

 spermatozoid mother - cells 

 arise. 



Fig. 74. (After Luerssen.)— Bursting of 

 the antheridium and escape of the 

 spermatozoids. a», antheridium; m.e, 

 spermatozoid mother-cells; sp, sper- 

 matozoids. 



Fig. 75. (After Strasburger.)— Mature 

 archegonium, showing the oosphero 

 (o), the neck (x), and mucus (»») is- 

 suing from the mouth of the canal. 



