200 PROFESSOR E, RAY LANKESTER, 
Metschnikoff supposed (but did not demonstrate) the aperture 
in the preeumbral lid is an orifice of invagination, by which 
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end. Endoderm. 
the sub-umbral cavity and the perforation of the manubrium 
have been brought about. In the latter case an important 
but readily intelligible difference between Limnocodium and 
Geryonia would be established. 
