1899 - 1900 .] Mr Crawford on Rectal Gland of Masmobranchs. 59 
Consideration of Function. 
With reference to the probable function of the organ I have 
attempted to describe, several theories, more or less vague, have 
been presented. Monro, in the original notice, was of opinion that 
the organ was a secretory one, and Dumeril calls it “ a true secre- 
tory organ ” ; but neither offers any suggestion as to the probable 
nature of the supposed secretion. Leydig (5) compared its struc- 
ture to that of the glands of Brunner in other animals, pointing out 
that in the genus Chimaera, in which a true rectal gland, as a 
separate viscus, does not exist, glandular tissue is present in the 
wall of the intestine at a corresponding situation, while in those 
fishes which possess a rectal gland the intestinal wall is in that 
region devoid of such tissue. 
Home (2) compared the organ to the caecal pouches of birds, 
and Retzius on that account suggested the title Bursa Fabricii. 
Blanchard, while apparently demonstrating the hypoblastic 
origin of the organ, is of opinion that it is analogous to the anal 
or circumanal glands of some vertebrates, and prefers the name 
“glandula superanalis ” to “ rectal ” or “ digitiform.” 
But, as Howes points out, such an analogy is probably fallacious, 
since the circumanal glands are almost certainly derived from the 
epiblast. 
Hyrtle, as quoted by Howes, supposed that the function was 
one accessory to reproduction, basing his belief upon a fancied 
increase in size of the organ in animals whose oviducts contained 
eggs, and upon his failure to detect food-stuffs within the organ. 
Howes could find no evidence to support Hyrtle’s theory, and 
observes that the identity of the structure in each sex is a strong 
objection to it. 
Howes, who notices and discusses these suggestions in an 
exhaustive paper, upholds the view that the function of the rectal 
gland is a secretory one, and concludes from this belief, and from 
its development and position, that it is to be compared to the 
vermiform appendix of other vertebrates. In the conclusion of 
his paper he writes “ In the fact that the organ is a secretory 
one, we have, in the long run, a further point of agreement with 
the caecum coli and appendix vermiformis. The fact that the 
