152 Papers from the Marine Biological Laboratory at Tortugas. 



aberrants, ii specimens have oculars I, V, II insert (fig. 15), and one has 

 V, IV, II insert. In this specimen genitals 5 and I are fused, mechanically 

 shutting out ocular I from access to the periproct. 



The series of Tripneustes esculentus from Montego Bay is very interest- 

 ing from the point of view of ocular development on several accounts. The 

 specimens show a direct progressive increase in the number of oculars insert 

 and the relative percentages of the same from the youngest to the largest 

 series observed. In specimens fully matured, as regards this character, 

 and including from 90 to 132 mm. in diameter, they have as the dominant 

 character (40 to 43 per cent) the oculars I, V, IV, II insert. This is the only 

 locality known for this species, and it is the only recent species known' 

 in which four oculars reach the periproct as a typical character. In pre- 

 vious studies of Tripneustes esculentus, many specimens were tabulated from 

 several localities, but without detailed measurements of the size of the 

 specimens. As the material was from various sources, it is impossible to 

 go over it again to ascertain the sizes but it is fair to say that the material 

 was practically all adults. With this qualification it is interesting to com- 

 pare the tabulations of Tripneustes esculentus from the several localities from 

 which there was sufficient material to give any reasonable basis for con- 

 sideration. 



1 90 to 123 mm. diameter. 



As shown in table i, Tripneustes from Bermuda is characterized strongly, 

 61 per cent, by having oculars I, V insert, with 35 per cent I, V, IV insert as 

 progressive variants, also in 2 per cent I, V, IV, II, and 0.5 per cent all 

 oculars one insert as progressive variants. The aberrants are few, i per 

 cent, one specimen having I, V, II and one having V, IV, II insert. This 

 Bermuda lot is the most primitive of the species that I know of as regards 

 ocular arrangement in adults. 



Tripneustes from Florida has 46 per cent with oculars I, V insert, which 

 is still the dominant character, but with a lower percentage than at Bermuda. 

 As progressive variants, 29 per cent have I, V, IV insert, and 12 per cent 

 have I, V, IV, II. The aberrants are 12 per cent, all being cases of I, V, II 

 insert. Florida specimens, while having oculars I, V insert as the character, 

 have a lower percentage of this character and a higher percentage of progres- 



> In Acrosalenia pseudodecorala Cotteau, from the Bathonien of France, oculars I, V, IV, II are said to 

 be insert as a species character (Phylogeny of the Echini, p. 112). 



