240 
Holothuria Jloridana and Holothuria atra 
be slightly beyond the first-year I will use simply the general term young to 
designate the group. 
Mitsukuri, 1897, demonstrated that with advancing age the spicules in Stichopus 
japonicus change so much that "the form distinguished by Theel as var. typicus is 
only a stage in the growth of the species," and from the results of my work I 
would emphasize Mitsukuri's conclusion as to the important bearing such facts 
have upon the description of species and the classification of Holothuroidea. 
Ludwig, 1898, found in Phyllophorus urna that the spicules pass from an Elasipod 
larval stage to the typical generic type and then, in old age, to secondary rosettes. 
This autlior (189Sa) also proved in Cucumaria laevigata a change in the spicules 
with advancing age. Ostergren, 1898, believed that Holothuria aphanes represents 
the young of Holothuria ivipatiens. The spicules of the former type disappear in 
the larger specimens and then later are replaced by those peculiar to Holothuria 
impatiens. 
Of the 138 specimens available for this paper, 118 are H. Jloridana Pourtales 
from the Bahamas, the Florida Keys, Tortugas, Cuba, Porto Rico, Haiti, St Thomas, 
Swan and Curacoa Islands, Caribbean Sea, and 20 are H. atra Jager from Zan- 
zibar, Mozambique, Arabian Sea, Marshal Is., Samoa, Society Is., Tahite and 
Hawaiian Is. After completing this study, I have examined specimens from the 
Galapagos Is. now in the collection of Dr H. L. Clark, which thus extends the 
range of H. atra across the entire Indo-Pacific Ocean. 
Simon's Bay, at the Cape of Good Hope, the locality of Th^el's H. africana 
is beyond the reported limit of H. atra toward that of H. jloridana. Adopting 
H. africana as a synonym of H. floridana it would be interesting to learn whether 
this species occurs at any places between the southern point of Africa and the 
Caribbean Sea. 
To facilitate comparison, under each character studied I have placed side by 
side the values for adult and young of the biometric constants, mean, standard 
deviation or index of variability, and coefficient of variation, each followed by its 
probable error ( + ) and at the end the total range of variation of the character. 
The formulae as given by Davenport, 1904, were used. For graduated variates 
and integral variates with a class range of more than one, the classes are named 
from their middle values. For graduated variates with a class range of one, or 
less than one, the classes are named from their minimum values. The adjectives 
dorsal and ventral refer to the bivium and triviimi respectively. The data for 
H. floridana are presented first, then those for H. atra together with comparisons 
between the two species. 
In the summary are given the differential characters which define H. floridana 
PourtaMs and H. atra Jiiger and upon Avhich I base the re-establishment of the 
former as a valid species. Finally there is a brief resume of the additional facts 
concerning development, growth and variation in common for the two species and 
then such as are peculiar to each. 
