ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
191 
of Annelids can be shown in all cases to arise from a single pair 
of teloblasts ; at any rate, the case of Nereis shows that such may be 
present only in very early stages, and so be easily overlooked. In 
Polygordius it seems to be certain that no teloblasts of any kind are 
present, even in the youngest stages. On the other hand, the case of 
Nereis shows that it is not safe to assume the absence of teloblasts 
without following the development, cell by cell, from the very begin- 
ning, and that, whenever it is possible to make such a detailed study, 
we may pretty confidently expect to find teloblasts. In Mr. Wilson’s 
opinion it is not rash to predict that the secondary mesoblast bands even 
of LojpadorJiynchus will yet be shown to arise by teloblastic development. 
In a footnote the author informs us that, by a study of Hydroides 
dianthus, he has been able to discover that the head-kidney opens poste- 
riorly into the proctodaeum. Under a high power the canal can easily 
be followed from its beginning near the front end of the organ and along 
its outer dorsal border into the anterolateral part of the proctodaeum. 
This fact serves to remove all doubt as to the homology of the head- 
kidney of the trochophore with the nephridia of the Rotifera. 
Development of the Earthworm.* — Prof. R. S. Bergh gives a critical 
account of the different conclusions which havo been maintained in regard 
to the differentiation of the germinal layers in Lumbricus and other 
Annelids, and relates his own observations. From the most median of 
the four rows of cells described by Wilson the nerve-chain is formed, 
but in its development an epidermic nervous plexus of yet earlier origin 
takes part. The three lateral rows of cells form the circular muscu- 
lature, while the longitudinal muscles arise from internal muscle-plates. 
As to the nephridia, funnel and coil and terminal portion differentiate 
from a common rudiment which arises in the internal muscle-plates 
without any help from the epidermis. Nor do the successive nephridia 
have any connection with one another. Bergh is as strongly opposed 
as ever to the theory that Annelid nephridia are homologous with the 
excretory tubules of Platyhelminthes and Rotifers. The last part of 
Bergh’s memoir, which is characteristically critical, is devoted to main- 
taining that the entire germinal streak of Annelids is a unity funda- 
mentally ectodermic. 
Cutaneous and Muscular Systems of Earthworm.f — Dr. P. Cer- 
fontaine has an elaborate paper on the cutaneous and muscular systems 
of Lumbricus agricola. The body-wall is discussed under the heads of 
(1) cuticle, (2) hypodermis, (3) muscular layers, (4) peritoneal membrane, 
and in the discussion of the second of these the hypodermis strictly so called 
is considered separately from the clitellum and parts connected therewith. 
It is very probable that the cuticle is merely the result of the trans- 
formation of the superficial protoplasm of the hypodermic cells ; it is 
very regular in structure, and it may be supposed that the bundles of 
the cuticle result from a sort of keratinization of the in ter fibrillar sub- 
stance of the protoplasm ; the striae would then be the result of the 
more or less complete disappearance of the protoplasmic network ; this 
is the more probable, as swellings are often found at the intercrossings 
* Zeitschr. f. Wiss. Zool., 1. (1890) pp. 469 526 (3 pis.). 
f Arch, de Biol., x. (1890) pp. 327-428 (4 pis.). 
