ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
53 
As in previously described cases there was a complete duplication of 
part of the body, with the sole exception of one earthworm in which the 
nndodermal part was absent. The author suggests that the absence of 
the endodermal core leads us to doubt whether the ultimate explanation 
of metamerism is to be found in the idea that “ gut-pouches ” are the 
first steps. It is not yet determined whether the monstrous growth 
occurs in the adult or the embryo, but the balance of evidence is in 
favour of the bifurcation being produced in the adult. Experiments, 
however, made with the object of producing duplication, were all failures. 
Mr. Andrews thinks that there is no need to invoke the activity of 
any unusual amount or character of idioplasm ; no special manipulation 
of “ supplementary determinants” seems necessary if we apply the facts 
worked out for the cleaving ovum by Driesch and Wilson. 
Larval Stages of Chaetopterus.* — Prof. E. Beraneck gives an account 
of his observations on a larval Annelid, which appears to belong to this 
genus, found at Villefranche-sur-mer. He finds that from an early 
stage the metamerism of the parapodial region is marked by the appear- 
ance of parapodia, and this region is maintained without much modifica- 
tion to the adult state. The parapodial buds are well marked, and have 
numerous projecting setae, so that they afford evidence that the ancestors 
of these Annelids were errant forms. The anterior and ciliated regions 
acquire their definite external form much sooner than the post-ciliary 
region. The. larvae of the Chaetopteridae have an independent existence 
for a comparatively long time, and have locomotor organs in the shape 
of ciliary crowns and parapodia. The region of the latter extends, in 
the young, over about half the body, but in the adult it occupies only 
one-sixth. 
A comparison of the European with the American Chaetopterus shows 
that the hinder of the two mesotrochal circlets, which are found in 
Ohaetopterids during almost all their embryonic metamorphoses, appears 
latest. These larvae pass through a stage in which, like Telepsavus , 
they have only one circlet of cilia. The second circlet is doubtless a 
secondary acquisition, due probably to a more precocious segmentation 
of the hinder region of the larva. The ciliary circlets characteristic of 
larval Polychsetes have no absolute value from the phylogenetic point 
of view, and are not always comparable with one another. One and 
the same species may, in different stages, be successively mesotrochal, 
atrochal, and telotrochal, and the author urges that the mesotrochal con- 
dition of a larval Chaetopterus of some age has not the same morpho- 
logical significance as the similar condition in a quite young larva. 
Prof. Beraneck thinks that the Chaetopteridae form a distinct group, 
and represent a special phylum of the class of Annelids. Their ancestors 
were probably free, and, in becoming adapted to a sedentary mode of 
life, the hinder part of their body has been especially modified ; so great 
indeed is the change that the homology of the posterior and anterior 
segments is very difficult to see in the adult, though obvious enough in 
the young. 
Nephridial Duct of Owenia.']' — Prof. G. Gilson finds a pair, some- 
times two pairs, of very small nephridial funnels, lying in the posterior 
* Rev. Suisse Zool., ii. (1894) pp. 377-402 (1 pi.). 
t Anat. Anzeig., x. (1894) pp. 191-4 (5 figs.). 
