OCULAR AND GKMTAI, I'l.ATKS. 



117 



lucunter 413 specimens have ocular V alone insert, only four h* ocular I alone in-,n . -Uwi,,g 

 the strong dominance of this character. In the whole m,ml,,r (7M) ,-x:,i,,i,,,.,|. then BN l..n 

 two specimens, 0.3%, with an aberrant arrange.n,-,,t of ocular-. I,, one, oeillttl \ . IV are 

 insert, and in the other V, II alone reach the pi-riproH ftahles, pp. n;:<, n, i 



n 



Dl 



158- 



TEXT-FIGS. 158-161. Ocular plate arrangement in Echinometra lucunter (Linn<5). Hayti, West Imiini. All figures 

 X4. (Compare text-figs. 111-114, p. 115.) 



158. Length 41 mm., through 3, 1. R. T. J. Coll., 768. Oculars all exsert, an arrested variant. 



159. Length 55 mm., through 3, 1. R. T. J. Coll., 769. Ocular V insert, the typical charartrr. 



160. Length 52 mm., through 3, I. R. T. J. Coll., 770. Oculars V, I insert, a progressive variant. 



161. Length 41 mm, through 3, 1. R. T. J. Coll., 771. Oculars V, I, IV insert, an extreme prograwve variant. 



Echinometra van brunti is an interesting form as it is apparently the highest specie- of the 

 genus, judging from the ocular plates. In 76 specimens the typical character is to have oculars 

 V, I insert, which occurs in 72%. As arrested variants only 11 % have ocular- nil e\ 

 which is the character of E. mathaei; in 12 % V only is insert, which is the character of K. 

 lucunter; and in 4 % ocular I only is insert. As a progressive variant, 1 % have V. I. IV i; 

 It would be most interesting to get a large series of this species for comparative .study, hut it is 

 felt that the number seen is enough to give a fair basis for comparison. 



In Heterocentrotus mammillatus (35 specimens) 80 % have oculars all exsert .11% are pro- 

 gressive variants with ocular V insert; in one specimen ocular I, and in one oculars V. 1 are 

 insert. One specimen is aberrant with oculars V, II insert. In the nearly allied Hclcrocentrotus 

 trigonarius (47 specimens) typically, 60 %, all oculars are exsert; in 28 % ocular V is insert, in 

 4 % ocular I and in 9 % oculars V, I are insert. In Colobocentrotus alratus (82 specimens , !< 

 have all oculars exsert, and in 1 % ocular V is insert, as a progressive variant. 



The Echinometridae as a family is characterized by very close adherence to the rub 

 ocular arrangement. In the whole 1,222 specimens examined, only four aberrant- were found; 

 of these, three have oculars V, II and one has V, IV insert (tables, pp. 163, 164). 



Having considered the character of ocular plates in their relation to the genitals and to 



