406 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
all of the above species except I). darwinii and D. lowei While I), mulleri resembles 
I), lowei in many points, it differs from it chiefly in these important respects: 
(1) In shape: The capital nm of I). lowei is times as long as wide, while in 
D. mulleri the length barely exceeds the width. Darwin describes the capita lum as 
“much compressed. 1 In I). mulleri it is one-half as thick as long; little compressed 
as compared. with lepas. 
(2) The segments of the posterior cirri have in D. lowei eight pairs of main 
spines; in I), mulleri six pairs. 
(3) In size of plates: The plates of our species are much smaller and farther 
removed from one another. 
(4) The segments of the scuta are separated by an angle of °70 to 80°, instead 
of by an angle of 50°. 
(5) The carina of T). mulleri does not “extend up between three-fourths of 
the length of the terga” (or very rarely, at most), and the prongs, instead of being 
separated by an angle, as in D. darwinii , are united by an even curve (tig. 6). This 
latter point, however, may be subject to variability. 
D. darwinii is described by de Filippi (’61, p. 76) as extremely common as a 
parasite in the branchial chamber of Palinurus vulgaris , and is found in or near the 
Bay of Naples. The external resemblance to D. mulleri is very close, but striking 
differences exist between the nauplii of U. mulleri and those of D. darwinii as figured 
by de Filippi (’61a, tav. xm, fig-s. 10 and 11). I need mention onty that in his figure 
of the older nauplius (ibid., fig. 11) the frontal horns are still bent backward parallel 
to the body, and the spines on the appendages are no longer than those of the just- 
hatched nauplius (cf. figs. 10 and 11 of I). mulleri). Other differences in the life of 
the nauplii are referred to later. 
Those species of Dichelaspis having similar habitats to that of I), mulleri , and 
apparently occurring in considerable numbers, are D. darwinii on lobsters of the 
Mediterranean, I>. nejptuni on crabs of the Southern Pacific, and I), aymonini on 
spider-crabs of Japanese water's. 
SOME OBSERVATIONS ON THE DEVELOPMENT. \ 
The peduncle of mature individuals is generally found to be entirely, or in 
part, of a pink color, this color being due to the ova seen through the translucent 
integument. After the eggs have passed into the branchial chamber, where they 
are cemented together into a somewhat saddle-shaped lamella, the external pink 
appearance extends to the capitulum. Some idea of the condition of the eggs can 
thus be gained from a glance at the barnacle. 
Eggs found in the ovary, which is contained in the peduncle, are roughly 
spherical in shape. Before passing out of the ovary they attain a diameter of 
about 0.1 mm.; under a high power such an egg is faintly pink in color, appearing 
light yellow near the circumference. 
When laid the eggs are kept in the branchial chamber, where the first segmenta- 
tion stages are found. The cleavage begins as total and unequal. Eggs were observed 
* D. lowei Darwin. Madeira; attached to a rare braehyurous crab; very rare (Darwin, 1851-54). 
fin the terminology of the following description of developmental stages, Korsheldt A Heider’s text-book (’99, pp. 
209-219) and Hoek’s report (’84) have been followed. The figures and descriptions in the former are of Balcinus and of 
different species of Lepas, in the latter of a species of Lepas. 
