Regeneration in Clavelina Lepadiformis

1. The polarity of a developing isolated piece of stolon of Clavelina lepadiformis is the same as that of the zooid from which it came in the case of straight or simpiy branched pieces. In pieces with congested ampullary branches the original polarity is lost and a secondary polarity acquired. 2. The number of rows of stigmata formed during the development of a stolon fragment varies directly with the size of the fragment. 3. In very small pieces development may become arrested at almost any stage, the stage of arrest depending on the quantity of mesenchyme contained in the proximal region of the stolon piece. If sufficient is present to enable development to proceed to the formation of a functional heart, a circulation is established that includes food reserves in the distal part of the stolon and development proceeds to completion. 4. In shorter pieces, less than 0.4 mm. long, development or regeneration does not begin. The total failure to develop is correlated with the absence of a region of relatively columnar epidermis, and it is suggested that the area of columnar epidermis in pieces that do develop is a visible indication of the presence and extent of a morphogenetic field.