230 
MR. NEWPORT ON THE IMPREGNATION OF THE OVUM, AND 
at the settlement of the dispute about penetration, which has so long engaged the 
attention of physiologists. 
Mode of proceeding. 
I have elsewhere mentioned that I employed a glass cell to contain the egg whilst 
it was examined*, with the view of keeping it in one position, and preventing the 
movement derived from accidental causes : it is made of a section of a piece of baro- 
meter tube, from one-eighth to one-fourth of an inch deep and three lines in diameter 
in the clear, which is cemented on a plate of glass of convenient size. This piece of 
apparatus, which I name a tube-cell , is of a size sufficient to contain only a single egg 
after its covering is fully expanded. For the purpose of making an observation, the 
egg is to be placed in the centre of the cell, immediately after removal from the body 
of the frog, and before it has come into contact with any fluid ; by this proceeding 
the gelatinous envelopes adhere so firmly to the glass as to render the egg almost or 
quite immoveable, when the jelly expands on the subsequent addition of water. In 
order that the proper focal distance of high magnifying powers may be obtained, I 
commonly use a cell which allow r s the object-glass to be immersed in the fluid. 
As this cell admits light on every side, it is well adapted for viewing the penetra- 
tion of the spermatozoon into the egg envelopes when the microscope is placed ver- 
tically, and a strong transmitted light is employed. It is convenient also for viewing 
the egg laterally with a simple plano-convex lens of low power, with the view of 
observing the formation of the chamber above the yelk, or watching the cleavage of 
the yelk ; but the experience of some years has proved that the cell is not suited for 
the lateral examination of the egg with the compound microscope, owing to the 
thickness and the convexity of its wall. True, the passing of the spermatozoon into 
the external envelope, and even into the vitelline membrane, can be readily observed 
when the tube cell is employed in the upright position of the microscope, but I 
have been unable to follow satisfactorily the course of the spermatozoon completely 
through the yelk membrane in that position of the object, in consequence of the dark 
colour and opacity of the egg. 
To ascertain the fact of the impregnation of the ovum by penetration, it was then 
necessary to invent some means by which the egg could be examined laterally with 
the compound microscope. The great difficulty to be overcome was the tendency of 
the dark surface of the fecundated ovum to maintain a vertical position, with the 
consequent rotation or rather gravitation of the whole mass of the yelk, whenever 
there was any change in the position of the cell. I contrived for this purpose a cell 
or box larger than the one before described, which may be designated a cistern box ; 
and with it I could note all the changes that took place whilst the egg was quite 
undisturbed. This box resembles the animalcule cage of Mr. TuLLY-j-, since it is 
* Philosophical Transactions for 1853, p. 267. 
f A Practical Treatise on the Microscope, by John Quekett, p. 130, 2nd edit. 
