Heredity and its Bearings on Atavism. 133 
theoretically also possible if it be conducted in such a 
way as to ensure the presence of the same set of organs 
in each fragment. 
The sewwal propagation of unicellular individuals is also 
not difficult to understand, for it depends on the transmission 
of cell organs derived from two distinct and individual cells ; 
the smaller, more active, and starving one being the male 
cell; while the larger, less active, and overfed one is termed 
the female cell. 
That which is so difficult to understand in fecundation is 
the associated reduction in the number of cell organs. Thus 
in Spirogyra nitida each cell possesses four spirally twisted 
chlorophyll-bands, the fate of which, in conjugating cells, is 
highly interesting. The contents of one cell pass by a 
bridge-like junction into another cell; then a fusion of the 
nuclei occurs analogous to that of other sexual cells, but 
four out of the eight chlorophyll-bands soon degenerate and 
become used by the newly-formed cell or zygote, which in 
this way maintains the normal number of four bands. It 
is important to note, that the four bands which disappear 
always belong to the active or male cell, and this fact seems 
to mea further proof of the correctness of my hypothesis, 
that fecundation consists in the union of a starved cell with 
an over-fed one.t The starved or male cell in the instance 
under consideration, is the result of the inefficiency with 
which the chlorophyll-bands perform their function of pro- 
viding the cell with carbohydrates. 
Spirogyra is thus an example of the fact that im an 
offspring the various organs derived from two distinet cells 
rearrange themselves so as to fulfil their physiological function 
to the greatest mutual advantage. 
Amongst other cell organs transmitted from parent to 
offspring must be mentioned the attractive spheres and their 
corpuscles, the nuclear achromatin (both the darker peripheral 
and the paler perinucleolar parts, distinguished by Frommann), 
the nuclear chromatin segments, the nucleoli and endo- 
nucleoli. 
1G, Mann, The Embryo-sac of Myoswrus minimus, a cell study. With two 
plates. —Trans. Bot. Soc. Edin., 1892, p. 399-424. 
