160 W. B. BENHAM. 



vided with the usual dorsal sac in Somite iv. One of my series 

 of longitudinal sections is of a worm with buccal region 

 everted; the other series shows the buccal region withdrawn. 

 I have thought it worth while to append sketches of these two 

 phases, as I am not aware that such pictures have hitherto 

 been published. ^ 



Fig. 12 represents a condition of rest, though the upper lip 

 (a, a'.) is partially everted. The floor of the buccal region is 

 transversely folded, giving a tongue-like appearance. The 

 lining of this region (fig. 15) consists of large round nuclei 

 embedded in a feebly granular protoplasm. I cannot with 

 certainty detect the outlines of the cells, which are probably 

 cubical. The surface is cuticulated. It appears as if these 

 cells were capable of a certain amount of alteration in shape. 

 The epithelium between the lines " a and a' " in fig. 12 is 

 flattened with elliptic nuclei as in fig. 14. Now, in the everted 

 condition (fig. 13), not only is the region a a' lined by flat cells, 

 but nearly all the everted epithelium is similar to this and 

 graduates near the edges of the orifice into the more cubical 

 character shown in fig. 15. 



The true pharynx commences at c and d, and is lined by 

 tall ciliated epithelium, with granular contents and elongated 

 nuclei. These cells are about three times as long as, and much 

 narrower than, those lining the buccal cavity (see fig. 16). 



In fig. 13, representing the everted condition, a dorsal sac is 

 represented, opening close to the external orifice of the everted 

 gut ; this sac is a normal feature in the pharynx of earthworms, 

 and is not apparently represented in the state of rest (fig. 12). 

 But this is merely owing to the fact that the latter section is 

 more accurately median, whereas the former is inclined to the 

 median plane, so that the dorsal part of the worm is cut 

 through along a more lateral line than is the ventral region. 

 This dorsal sac opens into the general cavity of the pharynx 

 by a wide mouth along the middle line ; this mouth narrows 

 laterally and curves forwards, that is, the aperture of communi- 



1 But see Garmau ou " Diplocardia," iu ' Bull. lUiuois Stale Lab. of Nat. 

 Hist.,' iii, pi. i. 



