siiggestt'd that this aiiaiigcnu'iit luav sul)s(>!vo the purpose 

 of respiration, and the vascnlaT network wliicli surrounds 

 this reg-ion of the alimentary canal (PI. TI., tig. '2, oe.-:/.), 

 lends some support to such a view. 



Histohigically the (esophagus, like the rest of the 

 alimentary tract, is lined hy ciliated epithelium. 

 S([uee/.ed in among the ciliated cells (PI. IV., 

 Hg. •)) is a number of laige unicellular gland 

 cells, among which two, or jiossihh- three, types 

 may be distinguished. After staining with borax carmine, 

 followed by picro-nigrosin, many of these gland cells (PI. 

 lY., tig. o, /9) take a yellow stain. They appeal- to be full 

 of laige coarse granules. Others similarly gianulated, 

 though much less numerous, shew an intense crimson 

 colouration (PI lY., fig. 3, }f). P^xcept for the difference 

 in staining reaction, these two tyj)es are indistinguishable. 

 The greater number of the gland cells, however, present 

 a ditferent a])pearance. Their contents consist of a coarse 

 spongy network, which presents a slaty-piirple hue (PI. 

 I\ ., fig. •!, a). Whether these various types are in reality 

 d.istinct, or whether they re})resent difierent stages in a 

 single type, is a question which must be left for future his- 

 tological investigation to decide. 



Besides being found l)etween the ciliated cells, 

 these unicellular gland cells also occur massed 

 beneath the ridges of the (esophageal epithelium. 

 li seems feasible that these large glandular (esopha- 

 geal cells sup])ly the active juices of digestion, whilst tlie 

 intestinal region is more concerned with al)S()r])tion. The 

 moje granulai- of them bear a close resemblance to the 

 large unicellular glands of the integument which, as has 

 already been seen, are probably concerned with the 

 markedly acid skin reaction. Siu-h a fact lends some 

 supj)ort to the view that the (eso])hagus is derived from 



