CHORIO-ALLANTOIC GRAFTS. 



299 



the shell membrane due to its absorptive nature, resulted in no 

 incorporation in the membrane of the host, and consequently no 

 growth. I then tried transplanting the otic vesicle with the im- 

 mediately adjacent mesenchyme, a slightly larger piece of tissue, 

 and found that in -uch operations, though incorporation may not 

 be complete and the mechanical injury more or k--- extensive, 

 nevertheless, growth en-ued. The investing tissue trail-planted 

 at the forty-eijit hour -tage includes only me-enchynie and 

 somatic ectoderm. In .'.11 the operation-, the brain wall 

 removed from ilie trail-plain before it wa- |)l.iceil on ihe mem- 

 br.me of ho-t . 



Table II. is a i' "t 'I of ihe -uccessful growths of the auditory 



TABLI II. 



1 ' THE OTIC Kl 



vehicle. It will be noted that one of the-e i- from a donor of 

 thirtv--i\ hour- incubalion, but the embryo >ho\ved .1 more 

 a-l\anced Stage of dr\ elopmetlt than i- u-nal for (hick- of that 

 age. It corre-pomU more nearly to the fort \ -foiir-hoiii ,nd 



( oiiM'(|iientl\- a|)|)roache- the u>llal don, ir age, forty-ei^ht hour-. 



T\\o criteria are einp!'\ed in tin- identification of the par 

 growths obtained in grafts of the OtOCVSt. The illorph, .logical 

 arrangement of the \ ariui- -tructure- aid- -reatK". but owing to 

 the di-or-ani/atiot) j.re-i-nl in every case, this is -upjtlcmented b\- 



