Miscellaneous. 439 
fice to say that, according to the abstract which I have made of 
the account (probably incomplete) he kept of the arrivals, he caused 
to be removed from Rodriguez more than 30,000 land-tortoises in 
less than eighteen months. When we reflect on the small extent of 
the island, we cannot be surprised that these animals, formerly so 
common, have entirely disappeared; notwithstanding their fecun- 
dity, they could not withstand such means of destruction. 
That which we have stated concerning the tortoises must have taken 
place also with the land-birds. It is evident that the sailors would 
not abstain from pursuing and killing them. Those species whose 
undeveloped wings rendered them easy to capture, while the delicacy 
of their flesh made them sought after, must have been rapidly exter- 
minated. It is therefore unnecessary, in order to account for their 
extinction, to invoke changes in the biological conditions ; the action 
of man was amply sufficient, and was exerted there without impedi- 
ment and with more facility than anywhere else. It is still going 
on in many other parts of the globe; and we can already foresee 
the period when many wingless birds, large Cetacea, and certain 
species of seals and otaries will have been annihilated by man. 
—Comptes Rendus de ’ Académie des Sciences, May 10, 1875. 
On the Development of the Pteropoda. By M. H. Fot. 
The vitellus of the Pteropoda before fecundation is histologically 
a simple cell with a deposit of nutritive matter in its interior. This 
fecundated vitellus is destitute of membrane and nucleus. It is 
composed of a formative or protoplasmic portion and of a nutritive 
portion composed of a network of protoplasm, in the meshes of 
which the nutritive globules occur. In the centre of the formative 
part there is a star formed by the granules of the protoplasm ar- 
ranged in diverging straight lines. The rays of this star stretch to 
the limit of the formative portion ; and the nutritive globules arrange 
themselves in lines. 
After the egress of the so-called corpuscle of direction, a nucleus 
appears in the centre of the star, which is effaced in proportion to 
the growth of this nucleus. The granules and the globules of 
the vitellus cease to be in lines. Before each segmentation the 
nucleus disappears, to be replaced by two molecular stars which ori- 
ginate in its interior. The centre of each of these stars may be 
regarded as a centre of attraction ; and all the vitelline substance 
obeys this attraction. After segmentation, a nucleus reappears in 
the middle of each star, and the vitelline substance remains at rest. 
The result of segmentation, which differs little from the recog~ 
nized types of the Gasteropods, is the development of a nutritive 
portion, composed of three large spheres, and of a formative moiety, of 
transparent spherules. Afterwards the nutritive cells divide, pro- 
ducing a superficial layer of little cells, which in the end envelop the 
three large nutritive spheres and constitute the ectoderm. The 
fourth of the large central spheres, entirely composed of protoplasm, 
divides completely and causes a thickening of the ectodermic layer. 
This region corresponds to the lower extremity of the larva. The 
line of junction of the three nutritive spherules coincides with the oral- 
