ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
281 
following are among the most interesting of the observations recorded in 
the second part. The cuticle of Capitella has nothing to do with the vitel- 
line membrane, but is a new formation formed at the close of gastrula- 
tion when the vitelline membrane is thrown off In the anterior region 
of the embryo during the early stages the ectoderm contains numerous 
unicellular glands, which the author believes to be excretory and to 
functionally replace the absent head-kidneys. They diminish in size 
after the fifth day. After the throwing-off of the vitelline membrane, the 
larva is during the greater part of its life uniformly covered with cilia, 
u hich later disappear. A somewhat similar condition exists in Terebella , 
but is of much briefer duration. The prototroch in Capitella develops 
very slowly, and is not functional until the fifth day, and as soon as it 
has reached its full development it begins to degenerate and is partially 
cast (cf. Polygordius). Simultaneously with the prototroch there appears 
a ciliated area near the mouth, described by Hatschek as the “ ventral 
ciliated band.” This the author regards as a part of the typical trocho- 
phora, and he gives it the name of neurotrochoid. He agrees with 
Hatschek in regarding it as the remnant of the orthostomodaeum of the 
Otenophore ancestor. In the formation of the stomodseum there are two 
independent primordia, one for the stoma and one for the oesophagus- 
pharynx. This was also noticed by Kleinenberg for Lopadoriiynchus , 
and by Zelinka for the Rotatoria. The author explains it by the sug- 
gestion that the prostoma originally opened directly into the mid-gut. 
From this prostoma an ectodermal oesophagus grew out between prostoma 
and mid-gut. This structure developed into a protrusible pharynx or 
proboscis, and in consequence of its movements a new opening, the true 
stoma, developed, which opened to the exterior, and so forced the prostoma 
inwards. This hypothesis is held to explain the various conditions of 
prostoma and stoma seen in the development of different animals. It 
will be noted that according to it the stoma is phylogenetically younger 
than the oesophagus-pharynx. The author believes that the development 
of the nervous system does not support the view that the ventral cord 
arises from lateral nerves, but rather Goette’s suggestion that it is 
derived from an anterior jiair of ventral ganglia. The development of 
the Nebendarm seems to support the author’s view that this is to be 
regard^ as a Darmrinne. 
A s to the origin of the Annelids, the author believes that the trocho- 
phora has' a phylogenetic significance, and that it was derived from a 
Ctenophore-like form. The pole-cells of the mesoblasts (teloblasts) 
are derived from the sex-cells of the Ctenophore, and therefore arise 
neither in ectoderm nor in endoderm. The Turbellaria are not on the 
direct line of Annelid descent, but are derived from a trochophora-stage. 
Regeneration in Tubifex.* — Herr II. Haase has studied the regene- 
rative processes in Tubifex rivulorum Lam., with especial reference to 
the food-canal and nervous system. The fore-gut, with the exception of 
a small anterior portion, is regenerated from the endoderm, whereas its 
ontogenetic development is ectodermic. The hind-gut is regenerated 
as it develops, namely from the ectoderm. In regeneration the supra- 
oesopliageal ganglion arises from paired ectodermic proliferations, but 
these have, to begin with, a ventro-lateral position. The ventral cord, 
* Zeitschr. wiss. Zool., lxv. (1898) pp. 211-56 (2 pis. and 11 figs.). 
1899 v 
