W. Nicoll 
145 
probably not a few other cases will be discovered. The above-mentioned 
genus Haplocladus offers the further peculiarity that it has only one 
asymmetrical intestinal coecum instead of the usual symmetrical 
pair. 
Another important conti'ibution to the anatomy of the flat-worms 
was made by Goldschmidt (1909) and extended by Von Hofsten (1912). 
It relates to the function of the so-called shell-gland which has hitherto 
been believed to be the active agent in producing the material for the 
egg-shell. It has, however, been shown by these authors that this 
function is actually performed by the yolk-gland cells which contain 
the shell substance in the form of small droplets. This substance is 
liberated in the ootype and it is not impossible that the secretion from 
the shell-gland may have some influence in causing this liberation. 
It is further shown that the yolk-cells possess little nutritive function. 
The old question of the homology of Laurer’s canal in the Trematodes 
and Cestodes has been raised anew by Odhner (1912), who maintains 
that the original view of Stieda is the correct one and that Looss’ later 
view cannot be admitted. The latter view, which has received acceptance 
of late, is that Laurer’s canal in the digenetic Trematodes is the 
homologue of the functional uterus in the Cestodes. This is a view 
that does not bear very critical investigation and from the topography 
of the “ shell-gland complex ” Odhner concludes that the real homologue 
is the Cestode vagina. On the other hand, in the monogene tic 
Trematodes Odhner denies that the gastro-intestinal canal is the 
homologue of Laurer’s canal; he regards it as a structure sui generis. 
In certain of the Monogenea the functional vagina is undoubtedly the 
homologue of Laurer’s canal, in others it is entirely absent. This is 
not remarkable in view of the fact that Laurer’s canal is frequently 
absent in the Digenea. Odhner has also introduced the new term 
“ ductus vaginalis ” to designate the duct leading from the paired vaginae 
into the yolk-duct in the Polyopisthocotylea. 
An important contribution to our knowledge of the excretory system 
of Platyhelminths has been made by Willem (1910), while many new 
structural details of the Amphistomes have been investigated by Stiles 
and Goldberger (1910). The descriptive scheme advocated by Stiles 
has not found general acceptance and it is doubtful if it will be much 
used outside America. According to this scheme the Trematode body 
is divided into hypothetical zones and fields, bounded by lines passing 
through fixed points and the internal anatomy is described in relation 
to these. The terminology, it may be remarked, is not pretty, while 
