142 



ROBERT TRACY JACKSON ON ECHINI. 



oculars I, V, IV insert. It is interesting to see that in this far distant locality the same laws 

 of ocular arrangement hold as on the New England coast. 



In Strongylocentrotus franciscanus a very young specimen (text-fig. 150) has no genital 



Table of Development of Ocular Plate Arrangement in Strongylocentrotus drobachiensis, and 

 Variation of the same in one Locality {text-figs. 131-149, pp. 129, 132, 134). 



* Italic numerals represent percentages, Arabic numerals the number of specimens observed. 



