64 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
notes of Willemoes-SSuhm (76), who died during the voyage of the 
‘‘Challenger” before his studies were completed. His paper gives a 
very complete account of the history of the above mentioned cirripede 
from the Nauplius to the sessile adult, but only a short and fragmentary 
description of embryonic development. In some of the later embryonic 
stages the observations are quite correct, but the few descriptions and 
figures of cleavage stages are very inaccurate. 
The embryology of Pollicipes has been studied by Nussbaum (’90), 
but his account is somewhat fragmentary. 
Among the Rhizocephalan Cirripedia the only description of a complete 
series of embryonic stages is Van Beneden’s (’70) account of Sacculina. 
Further, one or more of the investigators already mentioned has 
studied the early development of species of the following genera of Cirri- 
pedia : — Conchoderma, Scalpellum, Tetraclita, Dichelaspis, Chthamalus. 
However, much of this embryological work has been fragmentary, and 
often superficial. 
The last, and by far the most important, paper on the early embry- 
ology of the Cirripedia was published by Groom in 1894. This contains 
a good résumé of the previous work on the subject, reviewing the con- 
tributions of the various investigators mentioned in the preceding para- 
graphs. Groom studied the embryology of five species, namely, Balanus 
perforatus, Lepas anatifera, L. pectinata, Chthamalus stellatus, and Con- 
choderma virgata. His observations on the later stages of embryonic 
development and on the larval stages were exhaustive. The study of the 
cleavage was undertaken secondarily, and was not investigated as accu- 
rately as were the later stages. 
The accounts of the early embryology of cirripides which were given 
by observers before Groom do not as a rule contain records of detailed 
observation, which alone could be used comparatively in a paper from 
the standpoint of cell-lineage. Groom reviewed well the general accounts 
of previous investigators, and brought their results into line with his own 
observations. In reviewing the literature I must necessarily deal pri- 
marily with Groom’s account, because he is the only investigator who 
has attempted detailed description of the early stages of cirripede 
development. 
III. Materials and Methods. 
The material upon which this paper is based was collected at Wood’s 
Hole, Mass., in the summers of 1894, 1895, 1898, and 1899. Prof. 
Harold Heath of Stanford University, Cal., has collected and preserved 
