88 Mr. E. R. Lankester on the Zoological 
influences animal movements, it usually operates on muscular 
tissue, though there are cases (among the Vermes) where 
all in Actinozoa, and has no reference to homology, as 
Mr. Kent must see on reflection. The development of the 
osculum into an aperture for the inception of masses of food 
18 quite conceivable, especially when we look at such a sponge 
as Prosycum. e must also remember that the currents di- 
rected by cilia in the Sponges and the contractile organs round 
the mouth of Actinozoa are special developments gradually at- 
tained by these two diverging stocks which their common 
parent possessed but in general outline*. 
second source of error in Mr. Kent's conclusions is that 
* Dr. Richard Greef has this year described, in ‘Kölliker u. Siebold’s 
Zeitschrift,’ a very simple form of marine hydroid ( Protohydra Leuckarti) 
quite devoid of tentacles or tentacular processes. a 
