OCULAR AND GENITAL I'L.VIT.S 121 



The five species of Toxopneustes all have typically ocular* I, V in-ert , hut tl,. ,,,i.|- 



erable variation shown. Toxopneustes maculatus (five specimens) has 80', with ocular- I. V 

 insert and 20 % with I only insert as an arrested variant. Toxopneiutes pileolus in .is -penmen- 

 has 92% with oculars I, V insert and 8% as arrested variants with I only insert. Trpneutte 

 semituberculatus in 25 specimens has 96% with oculars I, V insert and -I ' , am-.- ted with I only 

 insert, thus being more progressive than pikolus. The next two specie- -how arre.-ted variant-, 

 but also progressive variants, and in an increasing degree. 



Toxopneustes variegatus, from the West Indies and Florida (1,04:5 specimen-, all adult- . 

 has as the species character 90% with oculars I, V insert (text-fig. 184, p. 165). An arrested 

 variants, 1% have ocular I only insert, one specimen has V only in-ert. As progn 

 variants, 8% have oculars I, V, IV insert and 0.2% have I, V, IV, II insert; 0.8% are 

 aberrant variants. Of the eight aberrant variants, two have oculars I, IV in-ert. \ heing 

 excluded by the fusion of genitals 4, 5 as in text-fig. 144, p. 134; one has oculars V, II in 

 I being excluded by the fusion of genitals 5, 1 as in text-fig. 146, p. 134; and five speci- 

 mens have oculars I, V, II insert as in text-fig. 145, p. 134, a right-handed equivalent of Un- 

 typical progressive variant I, V, IV. The comparison of this species with the next. \vlii<-li i- 

 a close ally, is interesting. 



Toxopneustes atlanticus (A. Agassiz), from Bermuda, has been considered a synonym of 

 T. variegatus (Lamarck), but it is here considered a distinct species. 1 In Toxopneustes atlanticus 

 the species character of oculars I, V insert is taken on early, as usual, but the number of pro- 

 gressive variants typical of adults is taken on at a later stage than in any other sea-urchin 

 studied. I have therefore divided the material into three series: the smallest, 35 to l~> mm. in 

 diameter, which is still developing; a larger series, 45 to 60 mm., which is developed as regards 

 ocular arrangement; and a third series, 60 to 77 mm. in diameter, which includes the largest 

 specimens seen (table, p. 161). In the smallest series, 35 to 45 mm. in diameter (5S7 .-pcci- 

 mens), 81% have oculars I, V insert, a much higher percent than in adults. Of arrest. <! 

 variants 0.9% have I only insert, a small proportion, showing that it is fully developed in this 

 respect. One specimen, 0.2%, has ocular V only insert. As progressive variants, 16% have 

 I, V, IV insert, about half the proportion of adults, and 0.3% have I, V, IV, II insert, again 

 about half the proportion seen in large specimens. There are in this small' 

 aberrant variants, 2%. Of these, one specimen has oculars I, IV insert, four have V. II. -ix 

 have I, V, II, and one has V, IV, II insert. 



1 Toxopneustes atlanticus was described as Leplechinus atianticus by Mr. Agassi* (1863) on the basis of it slender spines. 

 The spines are long, slender, soft to the touch, and typically of deep violet color, although light \ mlrt or green spines oc- 

 casionally occur. In T. variegatus the spines are stout, rigid, and usually gray or greon. The iK-rixtomal plates are smaller 

 than in variegatus; the color of the test is violet, not green or gray mottled as in mriegatu*. The arrangement of ocular platoi 

 as regards insertness differs very much from variegatus, progressive variants bring morr numerous as here shown. 

 comparative characters are constant in the large series of each species observed. While these two species are vwy d 

 seems reasonable to consider attentions as distinct. 



