266 WILLIAM BLAXLAND BENHAM. 
(6) A disappearance of a part of the nephridium ; or 
(c) A shifting of the position of the pore. 
In the case of the male duct each of these modifications is 
exhibited. In the somites, in which the ciliated rosettes are, 
the external extremity of the nephridium has disappeared ; in 
the somites carrying the male pore, the funnel region of the 
nephridium is absent, whilst in the intervening somites both 
these regions have aborted, and a fusion of these various parts 
has taken place to form the more or less elongated duct. 
We are not warranted in supposing that these changes have 
actually occurred in the development of these forms; it is 
possible that the appearance exhibited is the retention of a 
condition such as is seen in Hatschek’s Polygordius larva. 
In the oviduct the intermediate portion between the funnel 
and the pore has become very much shortened and widened. 
Again, in the case of the spermatheca, the greater part of 
the organ has aborted, whilst the remnant has swollen to form 
a sac in most cases, though in those Perichetz, where the 
coiled appendix is present, this may perhaps represent the 
tubular, whilst the sac represents the vesicular, portion of the 
original nephridium. But it seems to me that there is much 
greater doubt and difficulty in the case of the spermatheca. 
[For in Microcheta, as will be seen, there are six or eight 
spermathece to a segment, each being separate and opening in 
a transverse line, more like the small sacs sae the 
spermatheca i in Pericheta aspergillum.] 
It is possible that there is a great distinction er. the 
vesicular portion and the rest of the structure; the former 
may be merely the invagination of the integument to meet the 
glandular secretory tube which itself has had a very different 
origin, as suggested by Lang in his researches on Planarians. 
The spermatheca would correspond then with this non-essential 
vesicular portion of the normal nephridium. 
