MALE FEKN. OOPHORE OR PROTHALLUS. 200 



B. A Neck, which is composed of cells arranged in 

 four rows, constituting together a cylinder or tube, one 

 layer of cells in thickness : this projects from the 

 surface of the prothallus, and incloses the cells (a) and 

 (5) of the central series, while (c) the oosphere is em- 

 bedded in, and surrounded by, cells of the cushion. 



At the end of the section more remote from the apex 

 may be found Antheridia. Select one fully developed, 

 and it will be seen to consist essentially of an outer 

 wall, one layer of cells in thickness, which incloses a 

 central mass of cells, the contents of which may be seen 

 to be rounded off, and to have assumed the form of a 

 closely- coiled spiral : these are the mother-cells of the 

 anther ozoids. 



By comparing carefully-prepared and well-cut sections, the 

 development of the antheridia and archegonia may be traced, and 

 in both cases it may be seen that they originate from single 

 superficial cells. In the case of the antheridia young stages of 

 development are to be found on sections through the lateral and 

 posterior parts of the prothallus, while young stages of develop- 

 ment of the archegonia lie near to the organic apex. Young 

 archegonia should also be observed from above in young pro- 

 thalli mounted with the lower surface uppermost. If drawings 

 be made of archegonia from both points of view, and of various 

 ages, a comparison of them will give a clear idea of the processes 

 of development. 



The dehiscence of the antheridia, the escape of the antherozoids, 

 and their movements, should be observed with particular atten- 

 tion in fresh prothalli mounted in water ; also the opening of the 

 apex of the neck of the archegonia : in both cases the process 

 depends upon a mucilaginous degeneration of cell-walls of the 

 inner cells, and a subsequent swelling by taking up water, and 

 consequent rupture of the outer walls. Further, the movements 

 of the living antherozoids may be followed, and the act of 

 fertilisation observed ; the antherozoids being arrested by the 



P 



