FUCACE^. 117 



an orange-red pigment spot, and are provided with two 

 lateral cilia of unequal length. In the ha- in aphrodite con- 

 ceptacles, or those containing both antheridia and oogonia, 

 the former are situated at the upper part, nearest the 

 mouth. 



The filaments formed in the female conceptacles remain 

 unbranched ; the oogonium originates as a short filament, 

 which is soon cut off from the parietal cell from which it 

 springs by a transverse septum, and as it increases in length 

 is again divided by a septum into two cells ; the lower 

 remains short and thin, and is called the pedicel-cell, the 

 terminal cell increases considerably in size and forms the 

 oogonium. During development the wall of the oogonium 

 becomes differentiated into two distinct layers, the proto- 

 plasm becomes coloured with phycophaein, and contracts 

 to form a single oosphere, as in the genus Sargassiiin, or 

 divides into four oospheres in Ascophyllum, or into eight in 

 Fucus. 



Fertilization takes place after the oospheres have escaped 

 from the conceptacle into the surrounding water. The 

 outer layer of the wall of the oogonium is ruptured at the 

 apex, and the inner layer, which yet remains intact and 

 enclosing the oospheres, protrudes, but for a time remains 

 attached to the torn outer layer by a point at the base, 

 which corresponds to the point of protoplasmic continuity 

 between the pedicel-cell and the oosphere. Eventually the 

 inner layer of the oogonium with its contained oospheres 

 breaks away and escapes into the water, where the enclosing 

 membrane disappears, and the liberated oospheres, at first 

 angular from mutual pressure, assume a spherical form and 

 remain from the first perfectly motionless, not being 

 furnished with cilia. The motile antherozoids that have in 



