1901.] NATURAL SCIEXCES OF PHILADELPHIA. 251 



fragmentation, allliougli the length and distribution of the frag- 

 ments differ on the two sides. No connection between the cord 

 and the pharynx can be determined with certainty, although the 

 proliferation attached to the dorsal wall of the "lateral recess" 

 is still present. 



Stage X. — Tailed toad of 15.5 mm. Fore and hind limbs well 

 developed. 



This stage very closely resembles the preceding, the most marked 

 differences being the greater autero-posterior elongation of the 

 processus quadrato-cranialis anterior and the associated greater 

 posterior rotation of the quadrate. The Eustachian cord, also, 

 is very distinct, particularly in its anterior and posterior portions. 

 In the region just back of the quadrato-hyoid articulation it is 

 greatly reduced and traceable only with difficulty. In several 

 places the cord shows a distinct lumen. There are no distinct 

 signs of a proliferation attached to the pharyngeal wall extending 

 toward the cord. 



Stage XI. — Tailed toad, 6.8 mm., tail 1.5 mm. Close of the 

 metamorphosis. 



The processus quadrato-cranialis anterior has now increased con- 

 siderably in length, so that it extends in a direct antero -posterior 

 direction as in the adult toad. The axis of the quadrate has 

 attained an almost vertical direction, but it still extends somewhat 

 forward, its distal, articular end being located under the middle or 

 posterior part of the eye. The hyoid still maintains its union with 

 the quadrate. More posteriorly, in the region of the auditory cap- 

 sule, the columella auris can be traced farther forward. At its 

 anterior, distal extremity it is prolonged forward as a dense strand 

 of cells, which forms a connection with the posterior surface of 

 the quadrate. Only the more posterior portion of the columellar 

 rod is formed of true cartilage, the anterior portion being as yet 

 only a dense, undifferentiated mass of cells. 



The most conspicuous changes which the tympano-Eustachian 

 tube has undergone since the preceding period have been asso- 

 ciated with the change of axis of the suspensory cartilages. As a 

 result of this the tympanic portion of the tube, together with the 

 annular cartilage, has moved backward to a region below the 

 posterior portion of the eye. The tube, as a whole, exhibits the 

 same fragmentary character as hitherto, and I have remarked here. 



