108 ZYGOPHYCE. 
Wittrock includes his single genus Gonatonema in the Mesocarpee as 
an agamosporous form, without ascertained conjugation. As an excuse 
for this he says :—‘‘If we attached importance only to the neutral or 
sexual nature of the spore formation, as some of the modern systema- 
tizing botanists do even in the lower Cryptogame, we should be obliged 
to form a separate family for it, which might not even be placed in the 
class of Conjugate. To me the accordance with Mesocarpee as to 
the vegetative cells and the formation of the spores seems too great to 
allow the separation of Gonatonema from this family. It may not be 
unnecessary here to call to mind that the class of Diatomacee@ in which 
the formation of spores is in general effected through conjugation, does 
also embrace some genera where the spores are formed neutrally.” 
At the risk of condemnation as a “ modern systematizing botanist,” we 
do not feel content to include this genus in the M/esocarpee, and have 
therefore relegated it to a separate family until more complete evidence 
is furnished as to whether it really should be associated with the Conju- 
gate at all, although its affinities seem to lie in that direction, All we 
are justified by the facts to assume is that itis an aberrant form, which, 
on the faith of its vegetative character may for the present be retained 
in proximity to the Mesocarpee until its relationship is better established. 
Genus 51. GONATONEMA. Witirock. (1878.) 
Spores (agamospores not carpospores) without conjugation, 
formed by biseptation of the mother cells, which latter are bent 
angularly, and alternately, at the point of fructification. 
Wittrock illustrates this genus by means of « species not yet ascer- 
tained to be British, but which he regards as congeneric with Hassall’s 
species hereafter described. ‘‘Its vegetative stage consists of cylindric 
cells arranged in a single row. The membrane of the cells is very thin, 
and consists of pure cellulose. The bottoms of somewhat older cells 
are gently curved inwards, which gives rise to a small lens-shaped room 
between the cells. The contents of the cells consist of (1) a parietal 
thin colourless layer of protoplasm; (2) an axile cholrophyli-coloured 
rather thick band of protoplasm (the single chlorophyllaceous body of 
the cell) which runs through the whole length of the cell, and which is 
most frequently more or less excavated at both ends of the cell; in the 
band of chlorophy]] occur the so-called ‘starch granules, in a number 
of 2 to 4; (3) a rounded nucleus, which has its place at the side of the 
chlorophyllaceous body, or very often in a small circular opening in the 
middle part of the band of chlorophyll; (4) small drops of oil, attached 
partly to the inner side of the parietal layer of protoplasm, and partly 
to the onter side of thechlorophyllaceous band; and (5) colourless cell 
liquid, which fills the vacuoles between the parietal layer of protoplasm 
and the axile chlorophyllaceous band. 
“In purely vegetative cells the chlorophyllaceous body is found to pos- 
sess the power of making free, and rather quick movements. This species 
thus gives a second instance of independent movements of chlorophy]- 
laceous bodies belonging to vegetative cells. 
“The formation of vegetative cells takes place by bipartition, exactly 
in the same manner as in the Mesocarpee. The cells destined to bring 
forth spores have always a very considerable development as to length. 
While the vegetative cells just formed by bipartition are only 5 to 6 
times as long as thick, the cells which are ready to form spores are at 
least 9, and more often 12 to 16 times as long as thick. A rather con- 
siderable increase as to volume, by development in length, does conse- 
quently take place in these cells before they are capable of falfilling 
their propagative purpose. 
