CURTIS: LITE HISTORY OF PLANARIA MACULATA. 557 
the normal fission I can find no evidence that the new parts develop 
by the transformation of highly organized cells to a simpler type 
which produces the new organs. My whole evidence would rather 
indicate that there exist in the parenchyma certain individual cells 
which can be distinguished from the parenchyma proper and that 
these are responsible for the new parts in regeneration and also for 
the sex cells of the reproductive organs. The exact nature of the 
histological changes concerned in the regeneration is, however, an 
extremely difficult one upon which to obtain absolutely unquestion¬ 
able data. 
The structure of the mature reproductive organs of this planarian 
is here described for the first time. 
The development of the reproductive organs is also described, the 
facts of which are summarized in the paragraph on page 554. 
A note is given on a stage in the embryology of this form to show 
that the adult pharynx does not originate at the place where the 
embryonic pharynx degenerates. 
