C. L. Edwards 
239 
from H. atra to the variety amhoinensis. My studies show that the characters 
given for the variety have no validity. 
B. Material and Methods of Study. 
The material subjected to a statistical analysis for this paper includes 138 
specimens from the collections of the U.S. National Museum, the Museum of 
Comparative Zoology, Harvard University, and my own series. For their courtesy 
in placing specimens in my hands for study, I desire to express my thanks to Dr 
Richard Rathbun, Assistant Secretary of the Smithsonian Institution, and Dr J. E. 
Benedict, Assistant Curator, Division of Marine Invertebrates of the U.S. National 
Museum; and to Dr Alexander Agassiz, Director, Dr W. McM. Woodworth, 
Assistant, and Dr H. L. Clark, Curator of Echinoderms, of the Museum of Com- 
parative Zoology, Harvard University. I would acknowledge my indebtedness to 
Dr Charles B. Davenport for his counsel, and also express my appreciation of the 
skilful and conscientious aid rendered by my assistant, Mr Hubert Dana Goodale. 
The various taxonomic characters have been analysed by the biometric methods 
whose development and application to biological problems are due so largely to the 
work of Francis Galton and Karl Pearson. In biometry it is important to separate 
the young specimens from the adult. In the Holothuroidea it is evident that both 
length and breadth combined in volume must be considered in judging the age. 
The formula, volume of cylinder = tt^?--, was adjusted to the more or less shrunken 
body of the alcoholic specimen and its natural departure from the cylindrical form, 
by the measurement of the volume of ten individuals in water displacement. It 
was thus found that the average actual volume is .50 per cent, of the volume 
estimated by the above formula. Hence I have used the formula ~~ to deter- 
mine the approximate volume of the specimens studied. Mitsukuri, 1903, pp. 13 — 
19, concludes that individuals of Stichopus japonicus Selenka taken during the 
spring and early summer divide themselves into three lots; (1) the adult, (2) the 
second-year young and (3) the first-year young. From Mitsukuri's tables, in 
which lengths and diameters are given, I find with the formula ~ — that the 
average volume of the "second-year young" of Stichopus japonicus is 113"99 c.c. 
Mitsukuri concludes "that Sticho2)us japonicus reaches the adult condition in two 
whole yeai'S " therefore the " second-year young," while not sexually mature, are of 
adult rather than young size. The average volume of the " first-year young " is 
43-16 c.c. 
In H. atra and H. floridana I have included in the adult category all of 50 c.c. 
or greater volume*, realising that such an exact line of division is, to a certain 
extent, arbitrary, and yet that it is near enough to nature to give in a broad 
manner the average adult characters for comparison with those of the first-year 
young. Since it is pos.sible that some of the specimens included in the class may 
* One specimen of //. iitra, volume 49'46 c.c. is given as adult. 
