Similar phenomena have been made out by Driesch in the development of the archenteron of the same forms. At the end of the normal gastrula period of the starfish embryo, there is produced from the inner part of the archenteron two outgrowths, or pouches, that later constrict off to give rise to the cœlom sac and water-vascular system. If the gastrula is cut in two in such a way that the inner end of the archenteron, _i.e._ the part from which the pouches develop, is cut off (Fig. 65, _C_), it is found that the piece containing the posterior part of the archenteron closes in, forms a new sphere, and from the present inner end of the archenteron (that has also healed over) a pair of pouches is produced (Fig. 65, _C_, lower row to right of _C_). These pouches have arisen, therefore, from a more posterior part of the archenteron than that from which the pouches normally arise. If the same experiment is made at a later stage, when the pouches have been given off from the archenteron (Fig. 65, _D_, lower row to right of _D_), no new pouches are formed. This means that after the archenteron has once produced its pouches it loses throughout all its parts the power to repeat the process, although these parts possessed this power at an earlier stage. It is a very plausible view that the result is directly connected with the formation of the normal pouches, although it is of course possible that some other change has taken place in the archenteron that prevents the formation of the pouches. In order to give as nearly as possible a consecutive account of the experiments on the eggs of the frog and of the sea-urchin, a number of other discoveries have been passed over. Let us now examine some of the results on other forms. Chabry, as early as 1887, experimented with the eggs of an ascidian. By means of an ingenious instrument he was able to prick and kill individual blastomeres. The results of his experiments were not described very clearly, and later writers have interpreted his results in different ways.[120] Chabry stated that he obtained half-embryos from one of the first two blastomeres, but his figures show, especially in the light of later work, that the embryos were whole embryos of half size, although certain organs, as the papillæ and the otolith, may be lacking.