July 13, 1882] 



NATURE 



253 



such as the Hornbill and Podargus have the palatines 

 meeting at the middle below. 



The quadrate is very huge in the Crocodilia, and is 

 fixed as in the Turtle and its congeners, and as in them it 

 forms the greater part of the tympanic cavity ; in Snakes, 

 Lizards, and Birds the quadrate, or pier of the lower 

 jaw, is movable. 



OtTJ 



X 



city 



c.litj- 



T'J X 



Fig. 2. x 10. 



Fig. 3. — Upper part of mandibular and hyoid arches of third stage {Crocodilus 

 palustris) outer view, i£ inch long. Letters as in Fig. 2, except co, 

 columella. 



In Salamanders the quadrate cartilage grows up to the 

 top of the skull, in front of the ear-capsule ; this part 

 is called the "ascending process ; the other fork runs in- 

 wards under the fifth nerve, and is either articulated to 

 or fuses with the basis cranii. 



In all lizards except the Chameleons such an ascending 

 process is found, but it is segmented off from the quadrate 

 and becomes ossified as the " columella," which supports 



ot.p 



irik- 



Fie. 3. *<? 



Fig. 3. — Same part of same species (fourth stage), 3$ inches long, as Fig. 2 

 (inner view); a.iy, cartilaginous annulus tympanicus. 



the roof (this is not the auditory columella, or stapes) ; I 

 call the former the " epipterygoid." In the Crocodile there 

 appears, very early, a forked process to the quadrate ; 

 here the upper fork is the rudiment of the ascending pro- 

 cess or " columella," and the horizantal fork is a rudi- 

 ment of the pterygoid cartilage, which is so large in 

 Sharks and Skates, and forms their upper jaw. 



The lower jaw of the Crocodilia corresponds with that 

 of the other Sauropsida — the other Reptiles and Birds, 

 being composed of six splint bones, and an ossification 

 of the articular end of the cartilage, " articulare inter- 

 num," which unites with the nearest splint, "articulare 

 externum," to form one bone, this, however, is pneu- 

 matic, the cartilage itself being hollowed out and com- 



■ty 



Fig. 5? 



r - 



7,7/ 



ler view). Letters same as last, 

 .si, medio-stapedial ; e.st, extra- 



Fig. 3a.— Part of same object as Fig. 3 (it 

 with addition of St, stapedial plate ; 1 

 stapedial; s.sl, supra-stapedial. 



municating by a tube with the cavity of the ear-drum. 

 That tube is called the " siphonium," and Prof. Huxley 

 (see Proc. Zool. Soc, May 27, 1869, p. 391) thought that 

 Prof. Peters had mistaken this tube for a rod of cartilage, 

 which the latter described (" Monatsber. Konig. Akad. 

 der Wissenschaft. zu Berlin," November, 1868, p. 59:) as 

 running directly from the auditory columella into Meckel's 

 cartilage. Such a continuity of the auditory columella 



y 



■iij 



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Fie. A 



X/0 



Fig. 4.— Same species as last (fifth stage, 4 i inches long), outer view. Let- 

 tering the same, with addition of si, siphonium. 



(stapes and incus in one) with the hyoid arch and the 

 endoskeletal lower jaw does, however, exist from an early 

 period, up to the middle of incubation. Prof. Peters' 

 observations were made upon small embryos, Prof. Hux- 

 ley' s upon ripe young ; the former observed rightly, but 

 his reasoning upon the facts seems to me to be quite at 

 fault ; Prof. Huxley had not the proper materials to work 

 upon, but his reasoning was perfect, and the truth of his 



