544 Scientific Proceedings, Royal Dublin Society. 



microscope during the greater part of the night that the stages in the 

 development of tlie oogonium were observed. 



The bursting out of the oogonial incept and the early stages of the forma- 

 tion of the oogonium take place quite rapidly, and are accompanied by the 

 rapid flow of protoplasm from the hypha which bears the oogonial incept, 

 and from its branches, into the developing oogonium. There is, of course, no 

 transverse septum dividing this hypha from t!ie oogonial incept at tliis stage, 

 and indeed apparently no such wall is ever formed, although ultimately the 

 funnel-shaped base of the oogonium within the antheridium usually becomes 

 choked with a kind of plug of highly refractive material, as shown iu fig. 17, 

 Plate XLIV. 



When the oogonial incept bursts out through the top of the antheridium, 

 the wall of the developing oogonium is very thin, and indeed remains 

 throughout slightly thinner than that of the antheridium. The ragged edges 

 of the fracture in the antheridium wall can clearly be seen with high powers 

 in the early stages; later on this margin appears to become somewhat folded 

 back or thickened, so that a beaded appearance is frequently presented. The 

 developing oogonium is usually rounded in outline, but cases have been 

 observed where the wall was considerably indented, and the outline 

 consequently quite irregular. 



Owing to the dense contents of the antheridium, it is not always easy to 

 see, in living material, the oogonial incept within it, but usually this is 

 possible with careful focussing. It can always be seen on fixed and stained 

 material. Figs. 12 to 16, Plate XLIV, illustrate stages observed in one case 

 in the development of an oogonium. The first figure was drawn about ten 

 minutes after the young oogonium had burst through the wall of the 

 antheridium, and the comparative rapidity of development will be evident 

 from the relatively short intervals of time which elapsed between the periods 

 at which the drawings were made. In some instances it was found impossible 

 to trace accurately the outline of a developing oogonium with an Abbe drawing 

 apparatus owing to the rapidity with which changes in size occurred. 



When the oogonium has attained its full size, the passage of granular 

 protoplasm into it ceases, and at this stage the hypha from which it has been 

 developed, as well as neighbouring hyphae, are found to be almost devoid of 

 contents, and, presumably owing to loss of turgidity, these hyphae may also 

 have shrunk considerably in size. This is the case with the hypha /;, 

 illustrated in figs. 15 and 16, Plate XLIV. 



During the later stages of tlie development of the oogonium, and usually 

 before its contents begin to contract from the wall, the contents of the 

 antheridium begin to disappear. Before this happens the antheridial hypha 



