PROGRESS OF MICROSCOPICAL SCIENCE. 301 
carried rapidly along the surfaces of the section blade, and then the 
finest possible sections may be cut with great ease. The consistence 
of nervous structures, when thus frozen, is really exquisite for section 
cutting, and the tissue remains rigidly adherent to the capped top of 
the cylinder. Perfect steadiness of the freezing chamber is ensured 
by soldering it to the microtome plug, and it can be readily removed 
from its position by throwing back the section plate, a movement 
allowed for by the hinge-joint (#).” 
The Siliceous-shelled Bacillarie in Diatomacee.—These are being 
described in the ‘American Journal of Microscopy’ (March and 
April),* from papers which originally appeared in the ‘ Lens,’ and 
which were translations by Professor Smith, of Kiitzing’s work on the 
Bacillarie. Strange to say, however, there is no notice of either 
author or translator attached to the paper itself. But in another 
part an editorial note explains this fact. To those who are unfamiliar 
with the original work, this translation must prove of interest. The 
last passages in the April number contain a very decided but well- 
merited attack on Ehrenberg for his habit of disregarding the work 
of others in establishing species. 
Reproduction of Rotifer vulgaris—An American, Mr. C. F. Cox, 
has been studying this subject with some success. He says that 
“My attention was called to the process of reproduction by seeing, 
in the larger rotifers, an extra ‘gizzard’ below the one to which 
each individual seemed properly entitled, and by observing the in- 
dependent movements of the imprisoned embryos. But a simple 
egg-shaped vacuole-like ovum is to be seen in every rotifer, even at 
its birth, I believe. Subsequently the embryo develops its ciliated 
lobes, its proboscis, its eyes, and its foot or leg, and for a short 
period before birth a slight ciliary movement may be seen, and 
a slow working of the gizzard. At this time its head is close to 
the gizzard of the parent, and the appearance is as if the fetal 
rotifer were actually sharing the food of the mother and remas- 
ticating it. This, however, finally ceases, and the foetus, generally 
with some difficulty, turns itself within the parent, in order to present 
its head first at the time of parturition. If the operation is inter- 
rupted, or the parent much disturbed, the foetus may turn back again, 
and this vacillation is in many cases repeated several times before 
birth is effected. Some writers state that the nascent rotifers ‘creep 
out of their envelopes, extend themselves, and put their wheels in 
motion, while within the ovary, but I am convinced that motion of 
the ‘ wheels’ is impossible at this time, both from the size and from 
the position of the young, and the rest of the statement quoted seems 
to me highly imaginary. The slight ciliary motion observable at this 
time is produced, I think, not by the large cilia upon the infolding 
head-lobes, but by a ciliary system lining the throat of the animalcule, 
analogous to the ciliary system which I have discerned in the throat 
* By the way, there appears to be some irregularity of publication about this 
journal. We have only to-day, May 8, received the number dated April. Is it 
published at the end instead of the beginning of the month? 
a2, 
