ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
457 
each of the two outside individuals of these four bears more individuals 
than does each of the inner individuals. New individuals are con- 
stantly being formed at the periphery of the fan and at about the 
same time, but on some branches only one new bud arises, and on others 
two. 
The normal architecture of the colony is obscured by inequalities of 
the surface on which it lies in the case of creeping forms like Mem- 
branipora , Lepralia , and Escliarella. 
Regeneration of Lost Parts in Bryozoa.* — Mr. S. F. Harmer has 
studied, especially in Crisia, the process of regeneration. It may take 
place in various ways ; an old zooecium may form a fresh aperture and 
again become tenanted by a polypide, or it may grow out into a rootlet 
or into a growing-point, which will, in course of time, give rise to a 
complex branch. If a rootlet is formed, it may become pretty long, and 
then either give rise to a fresh stem as a lateral branch, or it may, after 
a time, take on the characters of a growing-point, so that the new stem 
is the direct prolongation of what was at first an ordinary rootlet. The 
new branches formed from the stumps of old colonies are more commonly 
developed from the old joints ; sometimes from the lateral joints, at the 
points where old branches have been thrown off ; and sometimes from tbe 
axial joints, at the points where old axial internodeshave been lost. The 
broken surface of an internode has the power of developing a fresh 
growing-point, which ultimately gives rise to a new branch. 
In the lower parts of a colony of some species of Crisia the long 
tube that forms the ordinary aperture of the zooecium is often lost, when 
the part left is protected from further injury by a calcareous diaphragm 
which prevents foreign bodies from falling into the cavity of the zooe- 
cium. Such a zooecium contains a brown body but no functional poly- 
pide. Sometimes a polypide-bud is developed below the diaphragm ; as 
the bud developes the diaphragm becomes absorbed, and the mouth of the 
aperture again grows out into a long tube. 
Origin of Embryos in Ovicells of Cyclostomatous Polyzoa.f — 
Mr. S. F. Harmer has investigated species of Crisia , in which the mature 
ovicells contain a large number of embryos. These are imbedded in 
the meshes of a nucleated protoplasmic reticulum, which also contains a 
mass of indifferent cells, produced into finger-shaped processes, the free 
ends of which are from time to time constricted off as embryos. These, 
after developing various organs, escape as free larvae through the tubular 
aperture of the ovicell. The budding organ from which the embryos are 
formed makes its appearance at an early stage in the development of the 
ovicell. The supposed ovum is found in very young ovicells, imbedded 
in a compact follicle, and appears to give rise to the budding organ. 
The embryos are thus produced by the repeated fission of a primary 
embryo developed in the ordinary way from an egg. 
Fresh-water Polyzoa4 — Mr. A. Oka has studied Pectinatella gela- 
tinosa , a new species found in a pond at Tokyo, with the object of 
throwing light on some obscure points in the structure and development 
* Kep. Brit. Assoc., 1890 (1891) pp. 862-3. 
t Proc. C'amb. Philos. Soc., vii., pt. ii., 1 p. [separate copy]. 
X Journ. College of Science, Imp. Univ. Japan, iv. (1891) pp. 87-150 (4 pis.) 
1891. 2 k 
