lOO 



CONKLIN. 



[Vol. XIII. 



ing rows of cells I shall call the rosette series, a name suggested 

 by the word rosette, first used in this connection by Wilson to 

 designate the small apical cells formed by the third division of 

 the first quartette. The following table will show the cells in 

 Crepidula which correspond to the cross cells of Nereis : 



Nereis. Crepidula. 



Rosette Apicals 



Basals Inner Peripheral Rosette 



^ . , Y Outer Peripheral Rosette 



Terminals ) 



Diagram 13. — The cross in Nereis and Crepidula. — a, Nereis : the stippled cells are the mterme- 

 diate girdle cells (molluscan cross) excepting the posterior one (x^) which corresponds to the 

 " tip cell " in the gasteropod. The trochoblasts lie at the margin of the egg. (Wilson's Dia- 

 gram II. B.) — ^, Crepidula : cross cells (intermediate girdle cells of Nereis) are stippled. 

 Apical and rosette cells unshaded as in a. Trochoblasts around margin. — c, Crepidula: 

 shading as in 3 ; rosette cells and anterior trochoblasts divided. 



Inasmuch as the formation of the peripheral rosette cells 

 occurs late in the cleavage, I have not been able to find the 

 further division of the outer cells of the rosette series in Crepid- 



