REPRODUCTION. 



611 



connexion with the comparative structure of the antheridium 

 it may be mentioned that, in the Muscinese and the Vascular 

 Cryptogams, each antherozoid is developed singly in a mother- 

 cell. This is the case in some of the Algae, such as the 

 Characeae, Coleochsete, and Oedogonium, but in the others, 

 such as Volvox, Vaucheria, Sphseroplea, Fucus, the anthero- 

 zoids are formed in considerable numbers from the protoplasm 

 of one and the same cell. 



Fig. 68 (after Strasburger). (A) Archegonium of a Moss with antherozoids (8} : 



os oosphere. 



We have now completed the task of tracing the develop- 

 ment of sexuality and the differentiation of the sexual cells 

 from the first indications to the culminating point. Beginning 

 with the entirely asexual microzoospores of Hsematococcus, 

 we have passed through the imperfectly sexual cells of 

 Ulothrix and Botrydium, to the completely sexual piano- 

 gametes of Acetabularia ; and beginning again with the 

 entirely similar planogametes of Acetabularia, we have passed 



392 



