33S 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The details of the division of the cells of the blastoderm and yolk- 
endoderm show so mucli variation that the process may be termed 
irregular. These differences show well the morphological insignificance 
of the details of cell- division in the present case, for the Nauplii vary 
proportionately much less ; every one of the numerous bristles or spines 
of the Nauplius has its definite character and position, which are main- 
tained with surprising constancy throughout, and this though they must 
have been produced by epiblast cells of very different modes of origin 
and arrangement. 
Early observations (1869) of Van Beneden have been neglected, and 
the law which he deduced from them overlooked, yet it seems certain 
that in Cirripedes and Copepods the surface of the embryos on which 
the median longitudinal and transverse furrows appear, and which has 
been described as ventral, is really dorsal. The mesoderm of the 
Nauplius shows no trace of an arrangement into somites, and the body 
cavity is continuous from one end of the body to the other. The author 
believes that the appendages of the Nauplius are all of the same kind, 
and may represent, as Prof. Lankester contends, for Crustacea generally, 
primitively post-oral appendages. At the same time it must be noted 
that the first two pairs of appendages are never ontogenetically post-oral. 
Of the peculiar features of the Cirripede Nauplius, the most im- 
portant are the shape of the carapace, with its fronto-lateral horns and 
caudal spine; the presence and structure of the fronto-lateral glands; 
the size, shape, and structure of the labrum, and the structure of its 
axial gland ; the character of the setose region ; the structure of the 
appendages ; and the size and form of the tail. The perfect similarity 
which obtains in all the species examined by the author in the number, 
disposition and minute character of the very numerous bristles and 
other processes on the appendages of Nauplii of the second stage, 
demonstrates that the character of the appendages is a primitive one, 
actually possessed by the common ancestor of the Thoracica at some stage 
in its life-history. 
The permanence of such minute characters as the arrangement of the 
bristles on the appendages for the vast time represented by the Tertiary, 
Cretaceous, and probably, at least, part of the Jurassic periods, is highly 
remarkable, and well shows the slow rate of evolution which may take 
place in so highly specialized a group. 
The differences between the various larvae are next pointed out, and it 
is shown that most of them affect structures peculiar to the Nauplius, and 
lost by the adult. The author remarks that it is evident that the varia- 
tion in the Nauplii (and the same may be said of the ova and embryos), 
though always accompanying adult variation, has taken place in a 
perfectly distinct direction. Few, probably, of the other characters can 
be referred to larval precocity. 
Mr. Groom refrains from entering on a discussion as to the origin 
and meaning of the Nauplius-stage, since, as the late Prof. Milnes 
Marshall pointed out, the origin of this larval form is outside the group. 
Post-embryonic Development of Lepadidae.* — Herr C. W. S. Auri- 
villius describes the divergences in the development of certain deep-sea 
* Ofversigt K. Vetensk-Akad. Forhand., 1. (1893) pp. 657-76. 
