330 Cleland. — The Cytology and Life-history of 
of which was covered with small granules. With weak chromacetic I 
obtained similar results. In no cell was the central region intact, and in 
many cases it seemed entirely empty (Fig. 14 ), as figured by Wolfe, although 
more usually a part or all of the pyrenoid or central body remained in an 
ill-preserved or shrunken condition (Fig. 1 5 ), with occasionally a few other 
granules scattered about in the surrounding vacuole. Perfectly preserved 
chromatophores were only found in Flemming-fixed material. It is clear, 
therefore, that a pyrenoid-like structure exists in the centre of the chroma- 
tophore. In this connexion, it is interesting to note Schmitz’s (1882) state- 
ment with regard to the sensitivity of the pyrenoid of the Nemalionaceae 
and Bangiaceae : ‘ Bei diesen Algen namlich quellen die Pyrenoide bei 
Einwirkung von siissem Wasser, Spiritus, verdLinnete Essigsauer, u. s. w. 
auf, und vertheilen sich schliesslich vollstandig im dem umgebenden 
Losungsmittel.’ The material in the central region is probably only pre- 
served by the best fixing fluids. 
One should notice in this connexion that Kurssanow (1909) described 
material of N. lubricum both with and without the pyrenoid. He believed 
the absence of the pyrenoid to be a sign of degeneration and approaching 
death of the cell, which can be artificially produced by fixing in the labora- 
tory. He stated that material fixed in the field shows the pyrenoid, while 
material fixed in the laboratory shows none. He described a line of 
development from presence to absence of the pyrenoid which does not con- 
form in the least with the mode of development in my material and seems 
to me very doubtful. Kurssanow used as fixing fluids iodine in sea-water 
and von Rath’s fluid diluted ten times in sea-water. I obtained no difference 
in chromatophore structure between material fixed in the field and material 
fixed in the laboratory. Neither did I obtain any difference between the 
material fixed during the day and that fixed during the night. The nature 
of the fixing fluid used determined the only observed differences in the 
appearance of the chromatophore and pyrenoid. 
There has been much diversity of opinion as to the nature of the 
pyrenoid and the methods by which it works. Schmitz (1882) described 
the pyrenoid as a rather homogeneous mass which in structure is closely 
allied to nuclein. Although actively concerned in the manufacture of 
starch, it takes no actual morphological part in this process. The starch is 
deposited in the clear zone surrounding the pyrenoid. 
Meyer (1895) believed the pyrenoid to be crystalloidal in nature, 
serving merely as reserve food and taking no part in metabolism. 
Schimper (1885) considered the pyrenoid to be of the nature of a 
protein crystal, but believed that it took part in the manufacture of starch 
in essentially the same manner as described by Schmitz. 
Boubier (1899) likened the pyrenoid to a leucoplast and considered 
that not only the central body, but also the surrounding clear area, which 
