540 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
The change from this to the adult pharynx is the completion of the 
lumen and the breaking through of the mouth. The formative cells 
which have built the young pharynx lose their identity as such and 
their nuclei change during the next day or two into the smaller 
nuclei of the adult pharynx, some of them still retaining nucleoli 
such as are always present in the formative cells and often in the 
other cells of the body excepting the ectoderm. 
Tlie changes in the nervous system have been described by 
Bardeen (:01) and Flexener (’98). I have nothing to add to 
their observations. 
Regarding the close association between the formative cells and 
the gut, which was mentioned in the stage represented by figure 39 
(plate 15), I have these additional observations. At the anterior 
end of the gut in tail pieces where the median ramus grows out 
(pi. 9, figs. 5, 17), sections show a very intimate connection between 
the formative cells and the cells of the gut. The gut (pi. 13-15,. 
fig. 35-42, g') in well fed worms has, as is commonly known, the 
appearance of a syncytium enclosing vacuoles (y) and masses of 
digesting food. The outlines of the cells are difficult of demon¬ 
stration. Figure 41 (plate 15) represents a sagittal section through 
the anterior tip of the gut (see pi. 9, fig. 16). The anterior end i& 
to the right and the magnification is Zeiss x 2. The parenchyma 
syncytium with its own nuclei (gip) and also scattered forma¬ 
tive cells,are shown. Some of the last are removed from the gut, 
but there are many which ai’e closely applied to it as in the lower 
half of the figure and even extend up some distance into the gut 
mass. There are still others which are entirely surrounded by the 
gut cytoplasm and in their own cytoplasm show small vacuoles, a 
thing I have never observed in formative cells anywhere else and 
which seems additional proof that they are being added on to the 
gut by their cytoj^lasm fusing with the gut cytoplasm. Many of the 
gut nuclei show a nucleolus exactly like that of the formative cell, 
but since nucleoli are sometimes found in nuclei of various sorts in 
the adult and normal worms, one must not make too much of this. 
The cases where the formative cells, cytoplasm and all, are within 
the gut are the strongest link (see also pi. 15, fig. 39, g and s). I 
have observed formative cells seemingly quite surrounded by gut 
cytoplasm at other places than the anterior and posterior faces of 
the new median ramus. This is not so remarkable since manv small 
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