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XI.—A Monograph on the general Morphology of the Myxinoid Fishes, based on 
a study of Myxine. Part IV.—On some Peculiarities of the Afferent and 
Efferent Branchial Arteries of Myxine. By F. J. Cole, D.Sc. Oxon., Professor 
of Zoology, University College, Reading. Communicated by Dr R. H. Traquair, 
F.R.S. (With One Plate.) 
(MS. received November 21,1911. Read January 8, 1912. Issued separately April 1, 1912.) 
The first three parts of this work, on the skeleton and muscles, were published in 
the Transactions of the Society in 1905, 1907, and 1909. 
In 1905* I briefly drew attention to the existence of vascular papille on the 
afferent branchial arteries of Myxine, which had up to that time escaped notice, and 
which I then described in the following words: “In addition to the definite blood- 
vessels, Myaine possesses a system of large lacunar spaces, such as the extensive sub- 
dermal cavity, the spongy tissue of the head, the peribranchial sinuses, etc., which have 
been generally regarded as belonging to the lymphatic system. I have, however, long 
been convinced that these spaces were in communication with the blood vascular stream. 
JACKSON, in his work on the vascular system of Bdellostoma, mentions the passage of 
injection mass from the vessels into the lymphatics, but believes the connection between 
the two to have been an artificial one, since he does not find red blood corpuscles in 
the lymphatics in fresh and uninjected material. If this is true, then Myaine is greatly 
different, as blood is invariably to be found in the lymphatics in living material. 
_ Ewaxr, in his paper on the vascular peribranchial spaces in the Lamprey, correctly 
appreciates the situation, and explains the general appearance of blood in these spaces 
by connections between them and the internal jugular vein found by him. 
“T shall enter fully into the morphology of these spaces in my fourth part on the 
vascular system of Myxine. In the meantime I may mention that I have discovered 
projecting from the posterior surface of each afferent branchial artery, at the place 
where this artery enters the gill sac, one or more papille, and I have found these in 
every specimen which has been dissected for them. On cutting serial sections of several 
of these papille it is seen that the base of each is widely excavated, and is, in fact, an 
evaginated portion of the cavity of the artery, whilst from this excavation there passes 
to open on to the exterior one or more fine channels lined by epithelium. The calibre 
of these channels is usually only slightly in excess of the width of an average red blood 
corpuscle. The presence of these channels at once explains the appearance of blood in 
the peribranchial sinuses in the normal living fish, and it seems certain that there must 
be other connections between the blood-vessels and the so-called lymphatic spaces in 
other parts of the body.” 
* Anat. Anz. Bd. xxvii. pp. 325-6. 
TRANS. ROY. SOC. EDIN., VOL. XLVIII. PART I. (NO. 11). 34 
