THE GROWTH OF THE EMBRYO IN THE FROG. 
237 
be granulated throughout; the other, or nucleated body, was clear, and had a distinct 
granular nucleus on one side. The changes proceeded more rapidly in one of the 
eggs, but the bodies were the same in all. 
At l h 45 m the two bodies were passing in a straight line from the centre to the 
circumference of the chamber. The spermatic particles were fading away and 
becoming granulous. 
At two hours the nucleated one began to change; its nucleus dividing into two 
granular masses, each of these having a bright spot in its centre. The same change 
took place in the corresponding body in each egg. Towards the end of the third 
hour the two masses subdivided, so that four granular masses were present at the centre 
of the nucleated cell ; and in each a bright central spot became very distinct. 
The anterior or granular spherical body was still present, and had passed outwards* 
followed by the nucleated one, to about midway between the central canal and the 
margin of the chamber above the yelk : the same transference took place in all. 
Shortly after the completion of the third hour, it was noticed that the rate of 
moving towards the margin of the chamber became more rapid, and that the bodies 
had reached the margin in a direct line with the centre of the yelk surface* one being- 
still at a short distance before the other. When, on viewing the egg laterally, the 
line of transit corresponds to the line of sight, the change of place is not readily per- 
ceived, except the bodies go out of focus; but if their course is at right angles to 
the line of vision, then the movement is most marked and interesting. When the 
granular or foremost vesicle has arrived at the margin of the chamber, this space 
becomes further enlarged by a depression in the centre, marking the commencement 
of the cleavage of the yelk : granular remnants of the spermatozoa were still recog- 
nizable in the chamber. 
At 3 h 10 m the four granular masses in the interior of the nucleated body still 
cohered together, and seemed to be again subdividing. At this time the little heap 
of granules, which originally escaped with the spherical bodies from the central 
canal and remained at its margins, gradually enlarges into a number of small trans- 
parent vesicles, in which at first no nuclei are visible: in some of the eggs six or 
eight of these are to be recognized. In consequence of the transparency of these 
cells, they are not seen unless the eggs are examined in the way recommended ; but 
during the observation, some attain a third of the size of the spherical bodies. These 
vesicles usually remain in the vicinity of the central canal from which they came. 
About 3 h 17 m the first division of the yelk is indicated by two clefts which 
appear at the margins of the canal, and sinking into the substance of the yelk, 
gradually extend outwards. As the cleft is produced, I have constantly observed 
the spherical bodies sink into it, and become for a time more or less lost to 
view ; but they do not pass into the substance of the yelk, for they are readily seen 
in the triangular furrow between the halves, either by means of a reflector above the 
egg, or when the cleavage lies in the' line of vision by the usual mode. When the 
