Hatschek's pit

If the preoral (Hatschek's) pit be regarded as a gland, it has been suggested by v. Wijhe that it is comparable to the neural gland of the Tunicata, and that the ciliated groove is comparable to the opening of that gland, the dorsal tubercle, the edges of which are frequently drawn out in a manner very similar to the course of the ciliated groove of Amphioxus.