On the Pollan of Loucjli Neagh. 247 
irregular distances from each other. We find the ova in all stages of maturity, 
on the same branch at the same time ; and we seldom observe a specimen of 
the F. carbasea, during the months of February, March, and April, which does 
not contain numerous ova. The ova have a lively yellow colour ; and when 
they occur abundantly on a specimen or a part of a branch, they cause it to ex- 
hibit the same lively hue, which is very different from the dull spotted brown 
appearance which the branches present at other seasons. Cells are often ob- 
served on different parts of the branches, containing neither polypi nor ova ; but 
the fewness of these, and the great number of cells still containing only polypi 
at the season of generation, render it probable that polypi are regenerated in 
the empty cells after the escape of the ova. In the empty cells from which the 
ova have escaped, we frequently observe a few remains of the former polypus, 
lying at the place where the body of the polypus bifurcated, and where the prin- 
cipal connection seems to exist between the polypus and the axis ; we likewise 
perceive numerous monades and other animalcules busily employed in consum- 
ing the remains of the dead polypus. The ovum, even before arriving at ma- 
turity, exhibits very obvious signs of irritability, frequently contracting different 
parts of its surface, and shrinking backward in its cell ; the cilia on its surface 
are likewise observed in rapid motion within the cell, as in the ciliated ova of 
other zoophytes. The mature ova are often found with their small end pro- 
jecting from the opening of the cells, and their final escape is aided by the in- 
cessant vibrations of the cilia covering their surface, by the ova contracting them- 
selves in their lateral direction, by the waves agitating the branches of the flus- 
tra, and by the same incomprehensible laws which regulate the formation and 
growth of the ova, and the whole economy of this zoophyte." Edin. New. Phil. 
Journ. iii. 116-7. 
(To be continued.) 
III. On the Pollan (Coregonus pollan, Thompson,^ of Lough 
Neagh. By WILLLIAM THOMPSON, Esq., Vice-President of the 
Natural History Society of Belfast. 
ff IN September last a comparison of the Lough Neagh Coregonus 
with the Vendace of Lochmaben, (whence I procured specimens 
