314 THE AMERICAN MONTHLY [Dec 
their formation the deposition of chitin had not followed 
one line of cells the whcle way, but had changed from one 
series to another. fogs 
As regards the function of the lateral bands, I would 
suggest that, in addition to strengthening the ephippium 
as they evidently do from their position almost directly 
over the egg, they may also help to keep the free edges 
of the valves more closely in contact than might other- 
wise be the case, Such a result would certainly follow 
if the ends of the bands, by their elasticity, possessed the 
power of pressing inwards and carrying the free marging 
= SO a 
