656 
ME. W. K. PARKER ON THE STRUCTURE AND 
Common Frogs and Toads; and the larger young are less than the Toad when its 
columella is first a cartilaginous rod (Plate 55. figs. 6-8). 
But in these young Pipce, with the body so little longer than that of the early embryo 
(figs. 1, 2), the columella is as perfect as it is in our common kind at the end of the first 
autumn. Supposing, as I do, that the stapes was solidified first, yet there was little 
time lost in either ; thus this type begins to break down that want of synchronism in 
the development of the upper and lower rods developed as parts of the “ 2nd postoral.” 
Another matter of importance in this type is this, namely, that the stapedial fossa is 
nearly obliterated in front, and that the almost contemporaneous stapes and columella 
are related to each other in a manner which is, to say the least, very Mammalian. Let 
the short crus of the Mammalian incus be merely the upper “ ear ” of a heart-shaped 
cartilaginous “ body ” ; let the “ os orbiculare ” ossify two fifths of a stout and somewhat 
outbent “ long crus,” the rest having its own centre, and stopping at the “ body ” ; lastly 
the fenestrate part of the stapes is to be arrested, — and then this supposed modification 
of the Mammalian ossicula would exactly correspond to what really exists in Pipa. 
But in this type the stapes is a neatly oval plug (Plate 61. fig. 6, st.), the flat face of 
which is outside, and the convex face placed inward, fitting into a funnel-shaped fenestra 
ovalis ( fs.o .), the open mouth of Avhich is the developed form of the long hollow (as 
though a piece had been torn away from the outer coat) which is seen in the first stage 
(Plate 60. fig. 3, fs.o.). Already the fenestra ovalis has been brought to the supero- 
external edge of the capsule, an elegant wedge of opisthotic cartilage finishing the outer 
margin above (Plate 61. fig. 6). In front of the fenestra the tegmen tympani (never 
large, see fig. 3) is receiving its squamosal investment ( sq .), and that in a truly 
remarkable manner. Behind, it is a film tiling the auditory eave ; it then creeps 
upwards to the cartilaginous selvage of the common bony plate, in which is seen the 
sweep of the horizontal canal ( hs.c .). The descending growth of the squamosal in the 
outer face of the quadrate (q.) is hidden by the columella ; but there is here an elegant 
anterior process (the long front part of the hammer-head in the common form of the 
Batrachian squamosal, Plate 54. fig. 7, sq,) ; this is growing into a cochleate process, and 
in this “spoon” the extrastapedial ( es.t .) and “annulus” ( a.t .) lies. The side of the 
auditory capsule being thus tilted up, the columella lies on the stapes, mandibular 
pier, and squamosal, and outside the diminished “tegmen it is well seen from above, 
although it is placed obliquely. 
The primary cartilaginous rod is pinched in at two places, marking off the three 
regions, namely, the interstapedial ( it.st .), the mediostapedial ( m.st .), and the extra- 
stapedial ( e.st .) ; in this, as in the other Aglossal Toad, there is no ascending supra- 
stapedial (“ short crus ”). The well-developed bony shaft covering the interstapedial 
region ( long in the Toads, and not cut off as a distinct separate cartilage as in 
the Frogs) is two fifths the length of the mediostapedial {m.st.) ; its fibres radiate over 
the unossified bulbous end of the bar which articulates with the stapes : in the adult 
(Plate 62. fig. 9) this is still better seen. In front of the longer mediostapedial shaft- 
