HUSCHKE. VON BAER 135 



chick l by the embryologist Huschke, a pupil of Oken. Like 

 Rathke, he found only three indubitable gill-slits, but he 

 noticed that the body-wall in front of the first gill-slit was 

 really composed of two arches, which were on the whole 

 similar to the gill-arches. The hinder of these two seemed 

 to him to be a horn of the hyoid, the front one, which was 

 bent at an angle, to be the rudiment of the upper and lower 

 jaws (p. 401). Between these two arches he found an 

 opening, just as between two gill-arches a gill-slit. This 

 opening led into the mouth-cavity, and according to Huschke 

 it became the external ear-passage. He discovered also 

 three pairs of aortic arches in close relation with the gill- 

 arches, so close indeed, that he did not hesitate to call them 

 gill-arteries, and to recognise their resemblance with the 

 aortic arches of fish. He traced, in part at least, the meta- 

 morphosis which these aortic arches undergo. This part 

 of his discovery he developed in fuller detail in a paper of 

 1828,- in which he gave some excellent figures. 



Shortly after Huschke's first paper, von Baer published 

 his views and observations on this subject in a short memoir 

 in MeckeFs Arc/iiv? In this paper he confirmed Rathke's 

 discovery, and described the slits and arches in the dog and 

 the chick. Both Rathke and he found gill-slits in the human 

 embryo about this time (p. 557). There were generally 

 present, he found, four gill-slits, and, as Rathke had 

 suggested, the first gill-arch became the lower jaw. Von 

 Baer also confirmed Rathke's discovery of the operculum, 

 assigning it, however, to the second gill-arch. He refused to 

 accept Huschke's derivation of the auditory meatus from the 

 first gill-slit. Von Baer saw what had escaped Rathke and 

 Huschke, that there were, not three nor four, but as many as 

 five aortic arches. 



1 " Ueber die Kiemenbogen und Kiemengefasse beym bebriiteten 

 Hiihnchen," Isz's, xx., pp. 401-3, 1827. (Read in Sept. 1826 to the 

 Versammlung der deutschen Naturforscher und Aerzte, then recently 

 founded by Oken). 



2 /si's, pp. 160-4, PL II., 1828. 



3 " Ueber die Kiemen und Kiemengefasse in den Embryonen der 

 Wirbelthiere," Meckel's Archiv for 1827, pp. 556-68. Also in Ann. Sci. 

 nat., xv., pp. 266-80, 280-4, 1828. 



K 



