Studies of Jamaica Echini. 145 



character are retained until individuals are about 20 to 25 mm. in diameter^ 

 after which they are typically a deep uniform black. As an exception, a 

 specimen 40 mm. in diameter was seen, in which all the spines were banded 

 as in youth. Frequently in immature specimens the older ventral spines are 

 banded when the dorsal spines, situated on the later-added and therefore 

 younger plates are quite black. In adults, no case of banded spines was 

 seen, but occasionally pure white spines are interspersed with the black, and 

 in a few cases observ^ed all the primary spines were white in the adult. 

 Whatever the color of the spines, the test is of a dark, uniform black in life. 



In the family of the Centrechinidse, Centrostephanus longispinus (Phil- 

 lipi), from the Mediterranean, in adults has spines which are banded 

 white and light brown, the pattern recalling those of young Centr echinus. 

 In Echinothrix calamaris (Leske), from the Pacific, the spines are very 

 variable in adults, being all dark, purple or green, all white, or banded; 

 great diversity may occur in the spines of one individual. In other families 

 of Echini, banded spines occur occasionally as species characters; they 

 are a feature of Ccelopleurus maculatus A. Agassiz and Clark, and are common 

 in species of the Temnopleuridae. 



In my previous studies of ocular plates and their variation in this 

 species, there was a limited number (no) of developing specimens, and 

 of these very few were really small. Of adults, 1,168 were examined from 

 various localities. With a good series of developing specimens from a 

 single locality, certain differences are brought out from the earlier limited 

 observations. There are also differences in the percentages of adult char- 

 acters from what obtained in the species as a whole from different localities. 

 In table 2 (page 156) are given the characters of developing series, and the 

 variations of adults of this and other species are considered. The aber- 

 rant variations are given in detail only under the consideration of the 

 species in the text. 



As to the developing series of Centrechinus setosus, in 50 specimens 

 from 4 to 15 mm. in diameter, all the oculars are exsert (fig. i). In 103 

 specimens 15 to 20 mm. in diameter, 78 per cent have all oculars exsert, 

 4 per cent have ocular I insert, and 5 per cent have ocular V insert. In 2 

 per cent oculars I , V are insert, and in 7 per cent oculars I, V, IV have reached 

 the periproct. Of aberrant variants of this size there are 5 per cent, one 

 specimen having ocular IV only insert; one having I, IV insert; two having 

 V, IV insert; and one has oculars I, V, I\^ III insert. It is interesting to 

 see that at this youthful period, while a high percentage have oculars all 

 exsert, many stages of development as regards the oculars are presented by 

 some of the specimens. Of the next larger size, 20 to 25 mm., 270 speci- 

 mens, 51 per cent still have all the oculars exsert; i per cent have ocular 

 I insert; and 16 per cent have ocular V insert; 11 per cent have oculars I, 

 V, and 17 per cent have oculars I, V, IV insert. In one specimen, 0.4 per 

 cent, oculars I, V, IV, II are insert. There are eight aberrants, or 3 per 

 cent; of these, i has ocular IV insert; i has I, IV, and 6 have oculars \^ IV 

 insert. 



