862 REPORT—1 890. 
(4) The bursting cells.—Many well-known epithelial cells are not essentially 
different from the silk-producing cells of Tenthredo. For example, the so-called 
‘ caliciform cells’ and other elements of the same kind. 
These cells are ordinarily furnished either with real vibrating cilia, or with a 
striated plate. 
They work in the same way as the cells with a striated plate during the first 
part of their life; but the secreted product soon accumulates within their proto- 
plasm in the form of one or more small masses. These increase gradually in size, 
and finally cause the cell membrane to burst. Their substance begins then to 
glide more or less rapidly into the cavity of the organ. 
The author has observed in certain cases, but not very often, for instance in the 
Triton cristatus, that this gliding mass was divided from the protoplasm, not by a 
thin and apparently structureless membrane, but by a striated zone entirely similar 
to the plate, of which it was the continuation. In this case he is inclined to think 
that the wall of the small cavity, as well as the striated plate itself, continues to 
allow the permeation of the secreted fluid. 
The intestinal villosities of certain coleoptera, for instance, the Cephalotes, con- 
tain in their middle part a series of transparent cells entirely different from the 
other epithelial cells. The nearer they lie to the digestive cavity, the larger they 
are, The last and largest one is often found in a state of destruction, which 
indicates that it has burst and given forth its contents. 
Another kind of cell which does not exactly burst is found in the intestine of 
many insects and myriapods. In these elements the secretion accumulates at the 
extremity of the cell until it forms there a considerable protuberance. These 
protuberances become pediculated, and finally they fall offinto the tube. Of course, 
they themselves are destroyed later, bursting and setting free their contents. 
These facts and many others which have not been mentioned induce the author 
to adopt the following view on secretion :— 
All the cases of cellular secretion are reduced to two general processes: the 
regular filtration and the direct pouring out. 
In the first process the substance permeates more or less rapidly through a 
filtering membrane. A thin and apparently structureless membrane is found 
ordinarily when the secretion is active and perfectly liquid, as, for instance, the 
secretion of the bile. A striated plate is often connected with the slower produc- 
tion of a more or less viscous substance. A viscous substance may certainly filter 
through the striated plate, and this plate, perhaps, plays then the part of an accu- 
mulating apparatus, out of which the substance may be cast quickly when a large 
supply is wanted. 
In the second process the substance does not pass through a filtering membrane, 
but is cast out directly. The excess of production over elimination causes the sub- 
stance at first to accumulate in a perceptible manner within the protoplasm, and 
produces subsequently the opening or bursting of the cell. The first process seems 
to be the primitive one, the most regular, and, in a certain sense, might be called 
the most physiological process of cellular secretion. 
6. On the Regeneration of Lost Parts in Polyzoa. 
By Stoney F, Harmer, I.A., B.Sc. 
It has long been known that, in the great majority of Polyzoa, a remarkable 
process takes place, by which, in each individual unit of the colony, the polypide 
degenerates from time to time, and becomes a ‘brown body.’ A new polypide is 
then formed as an internal bud from some part of the old zocecium, and soon 
becomes the functional digestive system of the latter. 
In Crisia, one of the Cyclostomata, not only are the polypides periodically 
renewed, but the zocecia themselves, or even whole branches of the colony, may 
be regenerated. his regeneration of parts other than the polypides is a subject 
which has hitherto attracted comparatively little attention. 
In the early spring, submerged stones from suitable localities may be found to 
be covered by the discoloured stumps of colonies of Crisia which grew in the 
