ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 223 
stated that the peribranchial sinuses always contained venous blood, and he investigated 
the connection of the lymph spaces with the veins by the injection of coloured fluid, 
although he states that this connection may easily be followed without any injection. 
He notes, as I have also done in Myxine, that blood may be clearly seen in the 
subcutaneous sinus in the living Petromyzon fluviatilis. 
Recent writers have paid very little attention to the peribranchial spaces of the 
Lamprey.* GEGENBAUR, in his text-book,t does no more than quote JoHANNES MULLER. 
Vocr and Yune}{ state that the sacs are completely closed and contain a viscid liquid, 
probably lymph, which coagulates in spirit into granular yellow masses. I take it the 
yellow colour is due, as in Myxine, to a certain admixture of blood. V1aLLEron does 
not believe the spaces to belong to the blood vascular system, and returns to the old 
view, aS we now know quite erroneously, that the blood they contain has extravasated 
into them through ruptured walls. Cort, § in his important paper on the blood vascular 
system of the young Ammocceetes, only mentions very briefly the system of blood 
sinuses. 
Mozxesko has conducted numerous experiments in the injection of the vascular 
system of Petromyzon, || but, apart from the fact that he says it is possible, he does not 
appear to have more than casually used the method of injecting from the heart. Hlse- 
where! he controverts VIALLETON’s statement that the peribranchial sinuses do not 
_ normally contain blood, and asserts that red blood corpuscles are found in all the lymph 
cavities. The sinuses cannot be injected directly wa the arteries, but are easily filled 
by injection through the veins. ‘The peribranchial sinuses, however, only communicate 
indirectly with the jugular veins, but in the case of some of them there is a communica- 
tion ter se. He regards the lymph sinuses of Petromyzon as blood-vessels and 
lymphatics at the same time. 
In Bdellostoma Jackson remarks:** ‘“‘] have observed in several cases a marked 
tendency for the injected carmine gelatine to escape from the blood-vessels into the 
surrounding lymphatics, which are very numerous and extensive. These lymphatic 
Spaces, especially the sub-dermal spaces in the caudal region and the peribranchial 
"spaces around the gill pouches, are usually found more or less injected, although the 
blood-vessels show no signs of over-distension. The lymphatic spaces around the 
vessels in the gill itself are also often filled. This condition may be interpreted as 
indicating that the capillary walls are unusually weak and permeable, so that the injected 
liquid passes through them, carrying blood corpuscles with it. That this process is not 
normal is shown by the absence of red blood corpuscles from the lymphatic spaces in 
life and in uninjected specimens.” In Myaine, as I have indicated above, the presence 
of red blood may easily be seen in the living animal in the subcutaneous sinus, and red 
* Op. Nestur, Arch. f. Naturgesch., 1890; Favaro, Atti Accad. sci. Veneto-trent.-Istriana, 1905. 
+ Bd. ii. p. 221. { Anat. comp. prat., t. ii. p. 460. 
§ Arb. zool. Inst. Wien, t. xvi., 1906. || Z. f. w. Mtkrosk,, Bd. xxvii. p. 248, 1910. 
I Anat. Anz., Bd. xxxvi. p. 618, 1910. ** Op. cit., p. 35. 
_ TRANS. ROY. SOC. EDIN., VOL. XLVIII. PART I. (NO. 11). 35 
