ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 709 
as the hard pseudo-cartilage, except that (1) the intercellular features are generally 
much feebler, and hence the softer consistency ; (2) the chambers are all smaller and 
of irregular shape—the regular peripheral chambers of the other variety being absent ; 
(3) the fibrous septa are not only weaker, but ramify irregularly throughout the tissue ; 
and (4) the nuclei are less coarsely granular (but otherwise similar). The soft pseudo- 
cartilage, in fact, bears somewhat the same relation to the hard variety as the soft 
cartilage does to the hard, whilst cartilage and pseudo-cartilage are connected up into 
a series by the hard pseudo-cartilage and the soft cartilage. Compare in this connection 
the histology of the superior and inferior chondroidal bars. 
EK. Tue Cranto-PHARYNGEAL FRAMEWORK. 
Under this generic title we may conveniently deal with that portion of the skeleton 
grouped around the mouth, pharynx, and central nervous system, and which exhibits 
par excellence that distinguishing feature of the mature myxinoid skeleton—the fusion 
of the parts into one continuous coherent whole. To what extent this has been formed 
by the fusion of independent elements, or whether it is more or less continuous from 
the first, we do not at present know. Our doubts on this point will, I hope, soon be 
set at rest by the speedy publication of the elaborate memoir which Dr L. Neumayer 
is now preparing on the development of the skull of Bdellostoma, based on material 
supplied by Prof. BasHrorp Dran. In the meantime, as far as Myaine is concerned, 
there is not a single independent cartilage in the entire skull, except a few of the 
nasal rings and the cartilage of the fourth tentacle. The division therefore into the 
following regions must, to a certain extent, be artificial in the present state of our 
knowledge. : 
“ Parachordal” Cartilages (fig. 2, p. c.).—For a considerable distance behind the 
skull there is a very gradually diminishing deposit of soft cartilage at the mid-ventral 
line between the elastica externa and the skeletogenous layer of the notochord. In 
Bdellostoma, according to J. MUuuEr, this is present as a detached ventral plate, and 
NEvMAYER also describes a detached ventral half-ring of cartilage behind the parachordals 
in Myxime. I have carefully searched for the latter in the sections of the 6°5 cm. and 
the 10 cm. Hags, but find no traces of the break. As the skull is approached this 
ventral deposit increases in volume, and extends upwards on each side of the chorda. 
At the same time similar deposits of cartilage appear in the dorsal region, and all of them 
imerease greatly in thickness and join up so as to form a complete ring round the 
notochord except for a mid-dorsal break (cp. fig. 2). This tube is thinnest at the mid- 
ventral line, and constitutes the soft parachordal cartilages ; but there is no break between 
them ventrally. Whilst the parachordals are increasing in volume the notochord is 
diminishing in size, and its membranes become gradually reduced. In front, the 
parachordals gradually merge into the hard cartilage of the auditory capsule, but the 
latter capsules are always separated in the mid-ventral line by a zone of soft parachordal 
