164 EDWARD A. BOYDEN 
that this is the place into which the cock injects his semen, and 
forces it in so that it is kept there. 
This idea of a receptaculum seminis was discussed at length 
by his student Harvey, and by de Graaf, the latter publishing 
the first picture of the bursa. Both denied the function ascribed 
to it by its discoverer on the ground that it was equally well 
developed in both sexes. Beginning with the middle of the 
nineteenth century, it was subjected to microscopic. examination 
and thereafter repeatedly studied, one group of investigators 
(Leydig and his successors) holding that it was purely a lym- 
phoid organ; another group (Stieda and his school) maintaining, 
on embryological grounds, that it was primarily a glandular 
organ. Following Kolliker’s description.of the epithelial origin 
of the thymus, in 1879, these views were partially reconciled, 
but gave rise to a new discussion as to whether the epithelial 
primordium is replaced by invading tissue or whether it is itself 
transformed into a reticulum containing lymphocytes. Most 
authors since Wenckebach (’88) have held that the epithelium 
undergoes transformation without invasion. Recently Jolly 
(715), in an elaborate summary of five years’ work on the histo- 
genesis, haematopoietic activity, and involution of the bursa of 
Fabricius, has advanced the theory that ‘‘the bursa represents 
an ancestral glandular organ, a cloacal caecum undergoing re- 
gression, which has become invaded by lymphocytes like other 
retrograding diverticula (the vermiform process of mammals and 
the intestinal caeca of birds), but in which, in view of a new func- 
tion, a particular adaptation has taken place between the (per- 
sisting) epithelial tissue and the (invading) mesodermal, lym- 
_ phoid tissue.”? In recognition of this symbiotic relation, Jolly 
would define both thymus and bursa as lympho-epithelval organs. 
Up to the present time, however, one must acknowledge that all 
attempts to analyze the function of the bursa or to find its coun- 
terpart in the hind-gut of other vertebrates have met with only 
partial success. 
Modern investigation of the cloaca may be said to have begun 
with the embryological studies of Gasser (’73—’80) and of Wencke- 
bach (’88), who reéstablished the view of Bornhaupt (’67) re- 
ewan: pe 
