38 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
lent to tlie secondary yolk-pyramids of Decapods. Each yolk-pyramid 
is, later on, converted into an endoderm cell by radial contraction in a 
centrifugal direction ; the archenteric cavity arises by the separation 
thus caused of the central portions of the pyramids from one another. 
The appendages are marked out first by two transverse furrows 
which do not extend on to the ventral surface ; the antennules, antennas, 
and mandibles are probably serially homologous, and all may represent 
primitively postoral appendages. The body-cavity of the nauplius 
arises as a mixed blastocoele and schizoccele, and soon forms a cavity 
continuous from end to end of the body. The nervous system shows 
from the first a complex structure, especially in the Balanids, where it is 
most specialized in the Balaninae. It seems from the first to include 
the ganglia supplying the antennules, as well as the represen! ative of the 
archi-cerebrum. The antennae and mandibles are respectively in close 
relation with the circum-cesophageal connections and subcesophageal 
ganglion. There is a most remarkable agreement between the nauplii 
of the different species in the general structure of the carapace, 
labrum, &c., and as this extends to the minutest detail in the case of the 
appendages it is clear that the features in question have been inherited 
from some stage of the common ancestor. On the other hand there are 
nearly always such differences in the new-laid ova as to allow of the 
separation of genera or even of species. 
The agreement in the development of Balanus and Lepas , stage by 
stage, shows that the ancestor of the Thoracica underwent a metamor- 
phosis similar to that of the present members of the group, and that, 
therefore, the Nauplius- and Cypris-stages were not evolved within it. 
Where variations occur, the variable features are the same in all the 
species ; the most conspicuous of them are those which affect the 
processes of cell-division. The size, shape, and colour of the ova and 
embryos of a species vary not inconsiderably, and though the nauplii 
differ somewhat in size and shape no conspicuous variations occur in 
structure. 
Vermes. 
a. Annelida- 
Anomalies of Segmentation in Annelids.* — Dr. C. J. Cori describes 
an abnormality in Lunibricus terrestris , one of the median segments 
being divided into two on the right side. He found similar intercalated 
segments in Hermodice carunculata, Lumbriconereis , Halla parthenopeia , 
and Diopatra neapolitana , and is inclined to refer the abnormality to 
very favourable developmental conditions which resulted in unusually 
rapid growth and consequent “ slips ” in segmentation. Possibly these 
cases may be of interest in connection with the theory of metamerism, 
for instance, in bridging the gulf between the irregular segmentation 
occurring in Nemerteans and the regular segmentation of Annelids. 
Earthworms from the Malay Archipelago. t — Dr. R. Horst gives 
an account of the earthworms collected during his travels in the Malay 
Archipelago, by Prof. Weber. In all twenty-one species were collected, 
* Zeitschr. f, Wiss. Zool.. liv. (1892) pp. 509-78 (1 pi.) 
t Zoolog. Ergebn. einer Reise in Niederlandisch Ost-Iudien, ed. by M. Weber, 
ii. (1892) pp. 28-77 (3 pis.). 
