THE @SOPHAGUS, STOMACHS AND INTESTINES. 417 
these Malpighian tubules, and I see no objection to ascribing 
an hepatic function to them. 
That the Malpighian tubes are the morphological representa- 
tives of the vertebrate liver is no contention of mine. If the 
“so-called’ livers of crabs, molluscs and other invertebrates are 
in future to be spoken of as pancreates, I suppose the Mal- 
pighian tubes should be so named. Fashions change, but it is 
difficult for one who has spoken of a gland for forty years as a 
liver, to see the impropriety of the term because some recent 
writers have suddenly discovered that it should be called a 
pancreas. 
That something may be said in favour of the term liver or 
hepato-pancreas does not seem doubtful to me; I know no 
vertebrate in which the cells of the pancreas are loaded with 
pigment and oil-drops, like those of the so-called livers of many 
invertebrates. 
I do not wish to discuss this matter further, as it is only a 
question of convenience. One term is as good as the other if 
the meaning is obvious, and I cannot conceive how, with this 
explanation, any difficulty can occur in understanding anything 
I have written on the subject. 
c. The Rectal Papille. 
The Rectal Papille are four hollow, conical bodies, two on 
each side, which project into the rectum. They are about 
‘75 mm. in length, and from ‘25 mm. to *3 mm. in diameter at 
their base. 
The wall of the papilla is composed of a single layer of large 
pyramidal cells, which are from 40 pu to 80 #, Or even *I mm. in 
length: their rectal surface is covered by a cuticular sheath, 
the outer sheath, continuous with the lining cuticle of the rectal 
pouch ; the inner extremities of the cells rest on a reticular 
connective pouch, the inner sheath, which bounds the cavity of 
the papilla (Fig. 52). 
The base of the papilla is covered by a layer of radiating 
muscle-fibres, which connect the inner and outer sheath. 
The cavity of the papilla is continuous with the body cavity ; 
28—2 
