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In this way we get the spherical, mulberry-shaped body, which we call the morula. The segmentation of the Amphioxus is not entirely regular, as was supposed after the first observations of Kowalevsky . It is not completely equal, but a little unequal.
Towards the end of 1866 two works of the Russian zoologist, Kowalevsky, who had lived for some time at Naples, and studied the embryology of the lower animals, were issued in the publications of the St. Petersburg Academy.
From the concordant observations of Kowalevsky at Naples and Hatschek at Messina, it follows, firstly, that the ovum-segmentation and gastrulation of the Amphioxus are of the simplest character.
It was a fortunate accident that Kowalevsky first examined just those larger specimens of the Ascidiae that show most clearly the relationship of the vertebrates to the invertebrates, and the larvae of which behave exactly like those of the Amphioxus in the first stages of development.
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