ORDER BRAKCHIOPODA. 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 

 setse 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 

 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. 



