30 HAROLD SAXTON BURR 



The operations were performed with a pair of iridectomy 

 scissors under the binocular microscope. During the operation, 

 and for the subsequent twenty -four hours, or until healing was 

 accomplished, the embryos were kept in a 0.2-0.4 per cent salt 

 solution. They were then removed to individual dishes in which 

 the water was kept fresh. When the larvae were ready to feed 

 they were removed to aquaria, balanced largely with Lemna and 

 Ceratophyllum. Records were kept of the history of each oper- 

 ated specimen. 



Care was taken in all of the operations not to injure the under- 

 lying forebrain, since any injury causes noticeable defects in the 

 telencephalon. 



In the series of experiments under consideration a large num- 

 ber of unilateral operations were performed. The material thus 

 obtained was killed at frequent intervals, the oldest larvae being 

 about six months old dating from the time of operation, and the 

 youngest only a few hours old. The killing fluid used was subli- 

 mate acetic. Ehrlich's Haematoxylin and Congo-red were used 

 to stain the 10 /^ sections. Normal material was subjected to 

 the same technique for controls. From the sections of the oldest 

 larvae a wax reconstraction was made of the rostral part of the 

 skull and brain by the Born method. 



The experimental investigations that have up to the present 

 time been reported on Amphibia, have tended to show that the 

 Anlage of the nose readily regenerates when parts are removed. 

 Bell ('07) goes so far as to assert that the complete extirpation 

 of the nasal anlage in the frog does not prevent the regeneration 

 of a nasal sac. In the few cases he reports, what be believed 

 was complete extirpation resulted in every case in a regenerated 

 sac, sometimes perfectly normal in size and structure, and in 

 other instances, smaller than its fellow. 



The present series of experiments started with the extirpation 

 of the nasal placode of Amblystoma. It became evident at once 

 that careful and complete extirpation of the rudiment was not 

 followed by regeneration. Of the two hundred and thirty- two 

 operations performed, only four showed any external evidences 



