150 Papers from the Marine Biological Laboratory at Tortugas. 



for the species in which oculars I, V insert is the adult local character, as 

 it is the youthful character in these immature stages from Montego Bay. 



The next larger series, 70 to 90 mm. diameter, 125 specimens, has one 

 specimen with ocular I insert as an arrested variant; 30 per cent have 

 oculars I, V insert. The latter, which was the leading character in the later 

 developing stages, has now passed into the phase of an arrested variant. 

 34 per cent have oculars I, V, IV insert, and this is the dominant character of 

 this age. As a phase it can be compared with a series of adults from the 



13 



14 



Figs. 10-14. — Normal ocular plate arrangement in Tripneustes esculenlus (Leske), 

 Montego Bay, Jamaica. All figures nearly X 2. 

 10. — Diameter 99 mm. Ocular I only insert, an extreme arrested variant. 

 II. — Diameter 114 mm. Oculars I, V insert, an arrested variant for the locality. 

 12. — Diameter no mm. Oculars I, V, IV insert, an arrested variant for the locality. 

 13- — Diameter ns mm. Oculars I, V, IV, II insert, the typical character for the locality. 

 14. — Diameter 106 mm. All oculars insert, a progressive variant. 



Bahamas in which locality I, V, IV insert is the typical character. Twenty- 

 eight per cent have oculars I, V, IV, II insert, which at this stage may be 

 considered a progressive character as it is at all other known localities for 

 the species. In 8 per cent the ocular arrangement is aberrant, all of the 

 ten specimens having oculars I, V, II insert. 



The next series, 90 to no mm. diameter, 200 specimens, has one speci- 

 men with ocular I only insert as an arrested variant (fig. 10), and one 

 specimen with ocular V alone insert. For ocular V only to be insert is a 

 rare variation in Tripneustes and is unusual in the family Echinida?. In 22 

 per cent oculars I, V are insert. This, which was the character of the later 

 developing series and is the character of adults at Bermuda and Florida, 

 has dropped considerably in its percentage as an arrested variant. In 24 

 per cent oculars I, V, IV are insert. This character for Montego Bay has 



