J892.] Phenomena and Development of Fecundation. 280 



on breaking out of the mother cell are seen to possess on their 

 anterior end an eye spot and two cilia, hy the rotation of which 

 they dart actively here and there. These are the so-called 

 miarozoospores. Finally two of them from different parents, hut 

 in appearance precisely the same, come together and coalesce. 



here only two uniting: while in the preceding stage there were 



5. The next stage in the development is the union of more 

 or less dimorphic elements. Both among plants and animals 



conjugation. Sachs says "this differentiation presents a most 

 complete series of gradations between the conjugation of simi- 

 lar cells and the fertilization of oospores by antherozooids, any 

 boundary line betwen these processes beine unnatural and 

 artificial." 



Cutleria, a seaweed of the branch Oophi/tu.i* an interesting 

 example of this stage. Here the female zoospores are large 

 and borne singly in specialized cells in the parent. These on 

 escaping, swim about for a time as do the microzoospores of 

 Ulothrix, after which they come to rest. The smaller anthero- 

 zooids now approach and conjugation takes place. In Cufhria. 

 then, we have a union of differentiated cells for the first time, 

 but they are yet both motile. 



6. As an illustration of the next stage where we find com- 

 plete differentiation as marked as in man, we select the Moss 

 plant. In the mosses, the male and female organs are com- 

 monly borne on different plants. The egg cell is located at 

 the bottom of a flask-shaped organ, the archegonium (fig. 

 18, a). The antherozooids (fig. 18, b) are small headed and 

 biciliated, approaching in appearance very near to the sper- 

 matozoa of higher animals. In fertilization the antherozooids 

 swim to and down the neck of the archegonium, at the bottom 

 of which they find the quiescent oosphere or egg cell with 

 which they fuse. The sexual cells of the moss plant, it is thus 

 seen, unite two and two. as in the last case, but the differentia- 



