confluens and the Morphology of the Ascocarp. 351 
of dense disks of fine granular cytoplasm such as were 
observed in connexion with the fusion of the tube with the 
antheridium. The receptive spot seems to be associated 
here as in the Alga egg with the bringing together and fusion 
of two cells which have not been in contact, and to be 
entirely unnecessary where the mere breaking down of the 
wall between two adjacent cells of the same structure is 
to be accomplished. 
We must note here at once that the processes described 
are not at all of the nature of a secondary fertilization. The 
presence of the receptive spot at the apex of the conjugating 
tube shows that the latter is an organic part of the oogonium, 
and that it is the fusion of tube and antheridium which is 
homologous with the fusion of egg and sperm in Oedogonium 
or Vaucheria , while the breaking down of the basal wall 
of the tube is a later development necessitated by the 
formation of a conjugating tube on the oogonium. However, 
under the conditions found in Pyronema both fusions are 
necessary for fertilization, and the question is merely one 
of homologizing the processes here with those in oogonia, 
where no beak-like conjugating tube is present; and as already 
noted, from this standpoint there can be no question that 
the possession of a conjugating tube on the oogonium is a 
later and more specialized condition than that in the Algae 
named, and that the conjugating tube is merely a portion 
of the oogonium set apart for the conduction of the male 
nuclei to the egg-nuclei. The nuclei of the tube are there¬ 
fore potential egg-nuclei, and their disintegration is physio¬ 
logically analogous to the disintegration of potential eggs 
as nurse-cells, &c., which is seen in so many cases in the 
ovaries of animals. 
We may conclude then that although we have two cell- 
fusions, i. e. first, the fusion of the antheridium with the tube, 
and second, the fusion of the compound cell so formed with 
the oogonium, these are not to be interpreted as two fertiliza¬ 
tions. The contents of the tube-cell are entirely passive 
after the fusion-pore has been formed, the real and only 
