Amœbocytes in Calcareous Sponges

Abstract

I THINK there can be little doubt that the Amœbæ referred to by Mr. Orton in NATURE of November 27 are not independent organisms, but constituents of the sponge from which he obtained them. I have been working for some time past at the problem of the origin of the germ cells in the common Grantia compressa, and have often found the flagellate chambers of the sponge crowded with am“boid cells, which can sometimes be seen actually squeezing themselves through the layer of collared cells. According to my observations, these am“bocytes are immature germ cells—;oogonia and spermatogonia—and they can often be seen undergoing mitosis in the chambers. A similar phenomena has been described in Sycon by Jrgensen. Possibly the am“boid cells squeezed out from the gastral cavity of Sycon by Mr. Orton were either of the same nature or else metamorphosed collared cells. The latter are very readily detached from their proper position in the sponge, and may then put out pseudopodia and come to resemble Am“b, as has long been known.