66 5 
and the Flag el lata. 
A large part of the work deals with facts and theories as to 
protoplasmic and chloroplastic structure, among which there 
is signalized the discovery of a blepharoplast at the insertion 
of the cilia in Chlorogonium. 
In studying the development of the zygote the author finds 
that the two chloroplasts fuse to form one, unlike their 
behaviour in Spirogyra (Chmielevsky, ’ 90 ), and that sometimes 
two pyrenoids may actually fuse together though this is not 
the rule. 
The paper concludes with a theory of sexuality, according 
to which the sexual reproduction in these primitive forms 
in which sexuality is only just evolved, is of the nature of a 
‘ reciprocal autophagy.’ 
This theory regards gametes as in origin ordinary vegetative 
individuals which have for certain reasons ‘ run down 5 so to 
speak, and have acquired by natural selection sexual affinity 
which corresponds to a sort of hunger by which they are 
driven to fuse with, i. e. consume, some other individual by 
which they gain nutritive substance, and also energy perhaps 
of some special nature as well as the stored chemical energy. 
This enables existence to be carried on briskly again. 
This way of looking at the matter fits many of the facts 
discovered by Klebs, such as that nutritive salt-solutions 
tend to avert sexual reproduction and bring on either partheno¬ 
genesis or a return to vegetative existence. 
The theory also demands that in primitive sexuality the 
fusing nuclei shall have the same number of chromosomes as 
the vegetative individual, and this is found to be so among 
the Chlamydomonads. The necessary reduction probably 
takes place on the germination of the zygote. 
Among more highly evolved plants the specializations 
to secure sexual reproduction mask the clearness of this 
interpretation, as when nuclear reduction becomes post¬ 
poned in the sporophyte until the gametophyte is about to be 
produced. Many other phenomena of sexuality are brought 
into line with Dangeard’s point of view in quite an interesting 
way. 
