DIV. I 



HORPHOLOQY 



199 



of certain cells termed GAHETANGIA, the process resembling the origin 



of the swarm spores. The product resulting from the conjugation of 



the gametes is called a ZYGOTE or ZYGOSPORE (Fig. 229 B 4). The 



facts are in favour of regarding the gametes as homologous with the 



swarm spores, from which they often differ 



only in their smaller size, and the game- 



tangia as homologous with sporangia. By 



this is meant that the gametes and game- 



tangia have been derived phylogenetically 



by the modification of swarm spores and 



sporangia. Such gametes are capable of 



active movement^ by means of cilia ; they 



seek one another in the water and unite 



in pairs (Fig. 229 B). 



The gametes, however, frequently 



FIG. 229. Ulothrix zonata. A t Asexual 

 swarm spore; Bl, a gamete; B2, 

 B3, conjugating gametes \Rk t zygote 

 resulting from conjugation, (x 500. 

 After STKASBURGER.) 



differ in size in the Algae and Fungi ; the 

 larger gametes, which contain abundant 

 reserve materials, are female ( ? ) and the smaller are male ( $ ). The 

 female gamete may be non-motile when it is known as an egg-cell. In 

 this case the small SPERMATOZOID seeks out and fertilises the large EGG- 

 CELL (OOGAMY). In the case of oogamy the gametangia are usually 



FIG. 230. Monoblepharis sphaerica. End of filament with terminal oogonium (o) and an antheridium 

 (a). 1. 'Before the formation of the egg-cells and spermatozoids. 2. Spermatozoids (s) escaping 

 and approaching the opening of the oogonium. 3. osp, ripe oospore, and an empty antheridium. 

 (x 800. After CORNU, from VON TAVEL, Pilze.) 



different. The cells in which the small naked spermatozoids arise 

 in large numbers are termed ANTHERIDIA (Figs. 230, 2 a; 231 a), 

 while those within which one or more egg-cells are formed are the 

 OOGONIA (Figs. 230, 2; 231 0,, <?). The egg-cell (OOSPHERE), which is 

 usually naked, frequently remains in the oogonium, in the wall of 

 which an opening forms (Figs. 230, 2 ; 231 o,, 0,,, o). Fertilisation of 



