Page:Proceedings of the Royal Society of London Vol 4.djvu/354

Rh teen days, by means of the funis, which is continuous with a second, ot external membrane, the chorion, which lines the interior of the shell. He states that the liberation of the embryo from the shell is not effected by any effort of its own, but by the expansive force of the growth of its body. He describes, also, another important fact which had been overlooked by previous observers, relating to the mode and place of origin of the new segment of the body in the Julidae. The new segments are always produced in a germinal membrane im- mediately before the penultimate segment, which segment, with the anal one, remains ])ermanent throughout the life of the animal. The production of the first set of new segments is commenced even be- fore the animal has burst from the amnion. After leaving the am- nion, the young Julus possesses six pair of legs, as stated by Savi and Waga ; but the author remarks, in addition, that, notwithstand- ing this, it is still inclosed in another tunic, the proper skin of the embryo, beneath which new segments are being formed, and which begins to be detached before the embryo has left the amnion. He suggests whether this may not be the representative of the proper tunic of the germinal vesicle. After minutely describing the em- bryo, and showing that its body is still formed of cells, he states that four pairs of new legs are forming beneath this tunic, and that, on the twenty-sixth day, the young animal throws off this cover- ing, and the legs are developed, and also the six new segments, to a further extent. The animal then takes food, the segments become developed to the same extent as the original ones, until the forty- seventh day, when it again changes its skin, new segments are again produced, and new legs to those segments last formed. In this way it passes through several changes, developing first segments and then legs.

One remarkable circumstance stated is, that the production of segments is sextuple in the Julidse ; but this does not hold in other genera, in some of which it is quadruple, and in others double ; but these peculiarities appear in all cases to be characteristic of each distinct genus. In conclusion, he confirms the observation already made by M. Gervais, that the number of eyes is increased as the animal advances in its transformations. The author concludes by stating that he proposes continuing these observations on the My- riapoda at some future period.

The paper is accompanied by drawings of the parts described, and of the successive changes which take place during the deve- lopement of the animal.

The Society then adjourned over the long vacation, to meet again on the 18th of November next.