in Dictyota dichotoma. 189 
nuclei, indicates that this body represents a substance which 
is utilized by the chromatin and not by the spindle-fibres. 
The development of the cell-plate or plasma-membrane in 
Dictyota belongs to the same type as that of Stypocaulon. 
No differentiated connecting fibres of any sort can be recog¬ 
nized. It seems that the apparently undifferentiated frame¬ 
work of the cytoplasm, consisting of large and small meshes 
in the immediate region of the cell-plate, is converted into 
a plasma-membrane. The behaviour of the cell-plate toward 
certain stains, and the character and behaviour of the 
cytoplasm in that region, immediately preceding the appear¬ 
ance of the plasma-membrane, as described in a foregoing 
paragraph, strongly suggest that the latter is not an actual 
transformation of the alveolar walls, but that the substance 
of the cell-plate is deposited by kinoplasm, which is present 
in the framework of the cytoplasm. The form in which this 
kinoplasm occurs here is difficult to determine. It does not 
matter, however, for our explanation, whether it takes on the 
form of a fibrous network or of alveolae. 
As has already been mentioned, this type of cell-plate 
formation is different from that in the higher plants where 
connecting fibres are present, yet it bears a closer resemblance 
to the latter, perhaps, than to. any of the several other 
methods known in the vegetable kingdom. It is not a 
cleavage as described by Harper ( 5 99) for the Phycornycetes^ 
nor is it in any way similar to the process of division by 
constriction that exists in either Cladophora or Spirogyra. 
Further investigation, especially in thallophytes and arche- 
goniates, will probably bring to light transitions between the 
several distinct types of cell-formation that are now known 
among Algae, Fungi, and higher plants. 
