80 IOWA STUDIES IN NATURAL HISTORY 
ger, it is hard to account for the almost universal evidence of 
regeneration shown in our specimens. Possibly it has partic- 
ularly aggressive enemies which bite off the rays or devour the 
whole animal, leaving but an occasional single ray to form the 
‘‘eomet star’’ frequently alluded to in text-books. But it may 
be simply a sort of alternation of generations by which a single 
animal may multiply itself by five without resorting to sexual 
reproduction. Whatever the explanation, I know of no other 
Kechinoderm showing the process of regeneration so completely 
as does this Linckia from Barbados. 
Lang, in his Text-book of Comparative Zoology, volume 2, 
page 506, says that in the Linckwdae ‘‘the arms become con- 
stricted off at their bases, after which not only does the dise 
regenerate the arms which have been east off, but each indi- 
vidual arm regenerates the dise and the other arms.’’ One 
cannot help speculating as to whether there is any relation be- 
tween the possession of two madreporie bodies and this excessive 
power of regeneration. 
The familiar Oreaster reticulatus is said to oceur at Barbados, 
but no specimens were secured by us. The fishermen told me 
that it feeds on the big conch Strombus gigas. Dr. W. K. 
Fisher, who will report on the Asteroidea of the expedition, has 
identified the following species from our Barbados material: 
Asterina folium was found under rocks near Pelican Island, 
where it resembled corraline spots on the nether side of stones. 
Rosaster alexandri, Lwidia barbadensis, and species of Plinthas- 
ter were also noted. On the whole, we were greatly disappointed 
at the searcity of Asteroidea at Barbados as compared with 
other parts of the West Indies. Perhaps the distance from the 
Continent has something to do with this paucity of forms, al- 
though this explanation lacks plausibility. 
Echinoidea.—The most abundant sea-urchin in this region is 
the white ‘‘sea-egg,’’ T'ripneustes esculenta, regarded as a very 
important source of food by the Barbadians. Some specimens 
grow to relatively great size, being six inches in diameter, al- 
though the average is only about three and one-half inches. There 
are two apparent varieties which do not seem to correspond 
to either sex or age and may occur side by side in the same area. 
One is entirely white, while the other has pure white spines, 
