ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
471 
muscles, and apparently to the dorsal longitudinal muscles, and the wall 
of the dorsal blood-vessel. 
The neoblasts are to be regarded as specialized embryonic cells set 
apart for the rapid formation of new mesodermic tissue immediately upon 
the fission of the worm. Their general interest consists in their bearing 
upon the subject of the germ-layers and of organic reproduction. Their 
presence seems to point to the independent existence of the mesoderm as 
a germ-layer. With regard to the latter subject, the presence of neoblasts 
in Naids and Tubifex appears to connect the processes of budding and 
of regeneration on definite structural grounds. 
New Earthworm.* — Mr. F. E. Beddard gives an account of the 
structure of the earthworm, whose remarkable action on the soil of 
Lagos we have already noticed. f It belongs to the genus Siphonog aster, 
and it is proposed to call it S. Millsoni. It is at once distinguished 
from S. segyptiacus by the smaller size of the remarkable appendages 
which seem to have the function of copulatory organs, and which are so 
rarely developed in terrestrial worms. 
Libyodrilus.J — Mr. F. E. Beddard also describes a new genus of 
earthworm from West Africa, likewise discovered by Mr. Millson. It is 
allied to Hyperiodrilus , but is unique among earthworms in that the 
oviducal pores are on segment XV. The author abstains for the present 
from offering any suggestions as to its particular affinities. It is called 
L. violaceus. 
Embryology of Nephelis.§ — Dr. 0. Burger finds that the cavitary 
system of Nephelis which ultimately incloses the ventral cord and the 
nephridial funnels is developed in the following manner. In each 
segment a pair of primitive segmental cavities is developed which fuse 
with one another in the middle of the germ-stripe and form a median 
cavity ; this gives rise to a continuous tube which traverses the whole 
length of the germ-stripe, and connects the lateral cavities not only with 
one another, but those of one segment with those of another. The 
primitive segmental cavities arise separately from one another by the 
cleavage of the two inner cell-layers of the germ-stripe which forms a 
somatic and a splanchnic layer. 
The author thinks that the lateral cavities — the direct descendants of 
the primitive segmental cavities — are the spaces which Prof. A. G. 
Bourne has described as only secondary, and as formed by the botryoidal 
tissue ; that, in fact, they are true coelom-spaces and homologous with 
the segmental portions of the coelom of Annelids. 
The two blood-vessels first appear, at a relatively late period, in the 
oesophageal region ; they are either developed from the remains of the 
primitive cleavage-cavity, which, extending actively forwards and back- 
wards, drive the tissues apart, or they arise for their whole length by 
cleavage which commences in the oesophageal region. Their develop- 
ment has nothing to do with the coelom or its layers. 
Not only do the facts of embryology and anatomy show that there is 
no communication between the blood-vessels and the coelom, but this is 
* Proc. Zool. Soc. Lond., 1891, pp. 48-52 (3 figs.). t See ante , p. 40. 
+ Proc. Zool. Soc. Lond., 1891, pp. 172-6. 
§ Zool. Jahrb. (Abtli. f. Anat.), iv. (1891) pp. 697-738 (3 pis.). 
