ORDER BRANCH IOPODA. 
343 
reddish, is punctated with white, like the eggs, and as yet makes 
no movement. It is not until the ninetieth hour, and when 
the eye has appeared, that the arms and the valves are elon- 
gated, and the foetus commences to move. At the hundredth 
hour, it is already very active. In fine, at the hundred and 
tenth, it differs from the young just born, only by having the 
setae of the oars glued against their stem, and that the tail of 
the valves is bent underneath, and received between the infe- 
rior edges of these pieces. Towards the end of the fifth day, 
the tail which terminates the valves in youth, and the setae of 
the arms, let go, like a spring, and the feet then only begin to 
stir. The young ones being then in a state to appear, the 
mother immediately lowers her abdomen, and they shoot forth. 
Some eggs, newly laid, and placed in a glass vessel, where 
they were closely observed by M. Straus, were developed in 
the same manner. Jurine has also given us, on the progres- 
sive changes of the foetus of daphnia, some analogous obser- 
vations, but which were made in winter ; and as the little ones 
were not disclosed until the tenth day, he had the advantage 
of being able more accurately to observe and define those 
developments. The first day, the egg presents a central bub- 
ble, surrounded with other smaller ones, with coloured mole- 
cules in the intervals. These molecules and bubbles appear 
i intended to form the organs by agglomerating, approximating 
to the centre, and finally disappearing. The sixth day, the 
form of the foetus begins to be defined: the seventh, the head 
and feet are distinguishable. On the eighth, the eye appears, 
as well as the intestine. The following day, the net-work of 
the same eye commences to be visible. The bubbles have 
almost entirely disappeared, with the exception of the central 
one, which occupies the alimentary canal under the heart. 
On the tenth, the development of the foetus is terminated, the 
little one issues from the matrix, and remains for a moment 
motionless. 
