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MR. AY. K. PARKER ON THE STRUCTURE AND 
below* I give a description of the branchial tufts in a larger species, as they have been 
little understood hitherto. 
At present little need be said of the cranial cavity ; it is, as yet, largely membra- 
nous; and the cartilage related to it is, from the notochord forwards, entirely facial 
in its origin ; and yet we have seen that the facial and the axial regions behave to the 
primordial membranous sac in a similar manner. 
The first bone related to the skull has appeared below the elongated intertrabecular 
(pituitary) space; it has the same shape, and is but little larger; this is the “para- 
sphenoid” (Plate V. figs. 2, 4, 7, pa.s.). The ear-sacs (cm.) being implanted in the 
side-walls of the now long straight cranium, at its posterior third, the cartilage, which 
might have sprung up along the whole upper edge of the “ investing mass,” is aborted, 
and only appears above, behind, and to some degree in front of the large periotic mass 
(Plate A 7 ", fig. 1). That which grows up directly from the auditory capsule in front 
is the rudimentary alisphenoid ( al.s .); that behind is the occipital arch (so., eo .); and 
that above is the pterotic ( pt.o.) : so we see that all these coalesced parts, first facial 
arch, periotic capsules, and alee of investing mass, behave in a like manner, and not 
otherwise than the symmetrical rudiments of a vertebra as they grow upwards to 
enclose the “ myelon ” and its fibrous sheath. Yet, morphologically, how diverse are 
these elements ! In the last stage (Plate IV. fig. 9) the periotic capsule was obliquely 
pyriform ; but now its contents have distended it in various directions, thus altering very 
much its original elliptical form. The semicircular canals and their ampulla; have done 
this (Plate V. fig. 3) ; and here it is shown that even on the outside their form can be 
seen ; and the capsule is hollowed between them, above. The horizontal canal ( h.sc .) 
has not only carried the capsule outwards in front, but it has also formed a ledge 
which projects outwards; this is the rudiment of the “tegmen tympani” (Plate V. 
fig. 4, t.ty.). We saw that the auditory sac was open in the first and second, and closed 
* On the Branch ice of Rana pipiens, Linn. 
The "whole series of arches is a deep suboval shell of cartilage open at the top, and placed so as to look out- 
wards and backwards. 
There are three clefts, two cochleate bars, and between these two widish rods with rather sinuous posterior 
edges. On the edge of the first cochleate bar there is a rich row of tufts (the Tadpole is “ Lophobranchiate ”), 
which arc principally ivithin ; they are well supplied with pigment-coated vessels, and are divided into short 
transverse groups. 
On the second and third narrower band-like arches the vessels, which are richly coated with pigment, are 
covered on the outer (lower) side, behind, with short transverse rows of rich tufts ; whilst from the anterior edge 
of the inner face of the bars shorter tufts, in transverse rows, grow upwards into the cavity of the shell-like 
branchial case ; these are not pigmented, and they are large in front. 
On the fourth arch the tufts are large and pigmented at the edge, and grow less and less in longer transverse 
rows on the inside of the spoon-shaped bar, and are not coloured black ivithin, but only where they hang down- 
wards at the free anterior edge. 
The result is a most rich and almost crowded crop of free depending tufts, and a less rich development within 
and above. 
The posterior edge of the third ray is sinuous ; the inner tufts are set on conical elevations of cellular tissue. 
