Anatomy of GorgonidtE. 103 



ous with that of the polyps. Homologically, the gullet lining 

 is ectodermal being generally considered the equivalent of the 

 ectodermal covering of the proboscis of a Hydroid, the gullet 

 of the polyp being simply an invaginated proboscis, the mouth 

 being then at the bottom of the gullet. 



It may be well to mention, however, that in this work the 

 homological proprieties will be dispensed with so far as the 

 mouth is concerned, and the aperture found on the oral sur- 

 face and between the bases of the tentacles will be regarded 

 as the mouth.' The mouth is not round but oval or oblong, 

 appearing indeed, more like a slit when the mouth is shut. It 

 is surrounded by a raised, thickened rim or lip.'^ 



Although probably identical homologically, the ectodermal 

 investment of the polyp and the lining of the stomach are 

 surprisingly different histologicall}^ as is shown in Plate I, 

 fig. 7) a and g. The former is composed of simple nucleated 

 cells of quadrate form, and the latter of cells which seem 

 to assume a somewhat follicular shape when in combina- 

 tion. Indeed the appearance is strongly suggestive of the 

 gastric follicles in the stomach of a frog for instance, and 

 would seem to indicate that the gullet is more than a simple 

 " atrium " as it is called by some authors, and acts as a part 

 of the alimentary apparatus. 



In none of the many sections examined, could I make out, 

 with any certainty, the aperture leading from the bottom of 

 the gullet into the body cavity. This aperture, as has been 

 said, is homologically the real mouth and was looked for faith- 

 fully, but in vain. 



It will be seen by referring to PI. I, Hg. 6, that the gullet 

 is a straight tube when the polyp is expanded, and thrown 

 into various convolutions when the polyp is retracted. 



A cross section of the polyp on a level with the gullet 

 will show the relation of the body wall, mesenteries, and gul- 

 let. As this is practically the same in all the species studied, 



1 "La bouche." Pouchet et Myfevre. 



2 "Le levre." Pouchet et Mv&vre 



