Memoirs of the Museum of Comparative Soilogy 
AT HARVARD COLLEGE. 
Vou. IX. No. 2. 
SELECTIONS 
FROM 
IMBRYOLOGICAL MONOGRAPHS. 
COMPILED BY 
ALEXANDER AGASSIZ, 
WALTER FAXON, anp E. L. MARK. 
LES ECHINOD E RIVAL A 
By ALEXANDER AGASSIZ. 
WITH FIFTEEN PLATES. 
CAMBRIDGE: 
Printed for the fMuseum. 
JuLy, 1883. 
