ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
205 
Vermes, 
a. Annelida. 
Development of Nereis Dumerilii.*— Dr. C. v. Wistingliausen finds 
that the cleavage of the egg of this Polychsete is total and unequal ; the 
ovum divides into four cleavage-spheres. At the animal pole four 
micromeres of equal size — the encephaloblasts— are constricted off. 
From these the cephalic ganglion and all the sensory organs of the 
head are developed. Three cleavage-spheres of equal size give off by 
constriction six micromeres, and from the largest sphere two large cells 
are given off — the somatoblasts ; from these the trunk, with the exception 
of the mid-gut and epidermis, is developed. The six micromeres do not 
take part in forming the organs, but only form the epidermis aud the 
larval prototrocli. 
The embryonic body is composed of two completely divided founda- 
tions; of the ventral, which is formed from the descendants of the two 
somatoblasts, and of the cephalic lobes which arise from the four eu- 
ceplialoblasts. Union of these two foundations is secondary merely. 
Development is direct. 
Sensory Nerves of the Earthworm.! — Prof. M. von Lenhossek, 
following Golgi’s technical method, has made an important contribution 
to our knowledge of tho nervous system of the earthworm. In Lumbricus, 
the sensory nerve-cells, which, like the spinal ganglion-cells of Verte- 
brates, give origin to peripheral sensory fibres, do not lie in the nerve- 
cord, nor in special ganglia, but occur in the skin. Thence each fibre 
extends to the nerve-cord and sinks into it, dividing in a Y-shaped 
fashion into an ascending and a descending branch, which extend longi- 
tudinally without further division, and end freely in the nearest 
ganglion. Lenhossek describes the supporting cells, mucus-cells, and 
nerve-cells of the epidermis ; the mucus cells arc but slightly modified 
supporting cells. So abundant are the nerve-cells that the skin may 
be described as a diffuse sense-organ. All the nerve-fibres which arise 
from the skin of a segment enter the corresponding ganglion, and the 
distribution is bilaterally symmetrical. From skin to nerve-cord the 
fibres retain their individuality, aud are almost without lateral branches. 
Most of them bifurcate in the nerve-cord, but the fibres entering on one 
side keep to that side. They end freely, and their length within the 
cord is such that they functionally command three ganglia. Lenhossek 
has thus been able to demonstrate a close parallelism between the nervous 
systems of Vertebrate and Invertebrate animals. 
Earthworms of Vienna Museum.^ — Mr. F. E. Beddard has a report 
on the collection of Earthworms preserved in the Vienna Museum, 
which he has had an opportunity of examining. The most important 
portion of the collection consisted of the types of Sehmarda’s species. 
Mr. Beddard finds that Hypogseon heterostichon should be placed in tho 
genus Anteus ; descriptions are given of the three known species of that 
genus, the affinities of which appear to bo mostly with Bhinodrilus. 
Perichaeta leucocycla turns out to be Megascdex cseruleus. Perichaeta 
* Mittheil, Zool Stut. Neapel, x. (1891) pp. 41-71 (2 pis.), 
t Arch. f. Mikr. Anat., xxxix. (1892) pp. 102-186 (1 pi.), 
j Anu. a ,d Mag. Nat. Hist., ix. (1892) pp. 113-34 (1 pi ). 
1892. 
Q 
