34 



Charles Zeleny. 



one from Woods Hole and the other two from Cold Spring Har- 

 bor, indicates the probability of some organic basis back of the 

 fact. This matter will come up again later in the discussion of the 

 development in ontogeny and during regeneration. At the same 

 time the considerable number of cases (fourteen [ ?] or 5.4 per 



Table IV. Hydroides diatithus. Position of Opercida (not including irregular 



ones). 



Table V. Hydroides uncinata. Position of Opercula. 



cent of the whole number) which do not come under either of these 

 groups will be taken up. 



Sixteen specimens of Hydroides uncinata were examined at 

 Naples. Of these ten, or 62.5 per cent, had the functional oper- 

 culum on the right and the rudimentary on the left, and six, or 

 37.5 per cent, had the reciprocal arrangement; a considerable 

 advantage in favor of the right-handed ones. 



