Anlage

Stockard has shown that, not only do anesthetics arrest the development of the intra-embryonic blood vessels in the embryos of Fundulus, at an early ontogenetic stage, but in such a manner that no doubt can now exist that, under normal conditions, these vessels are formed in situ by a concrescence of independent and discontinuous anlagen, and that their endothelium is derived directly from intra-embryonic mesenchymal cells.

Moreover, most species have a cirral pattern which - at least partially - closely resembles that of 18-cirri hypotrichs, including the formation from six (I-VI) anlagen.