226 



VITAL STAIKING AND MOR PHOGE NET I C MOVEMENTS 



HOTOCHODO 



^ECTOOERM 

 ^MRGIII OF ECTOOEKH 



1,1' 'v!?K»- I I ' ' I l\ \\/»NTER10R lURGlN OF 

 ^_^ HESOOERM 



-i-..- .' . ' "'''. 

 - »-.■"'■'• 1.- .-Yri 



MESOOERH 



CHOROA-HESOOERH 



BUSTOPORE 



to illustrate germ-layer relations in the late gastrula of an 



Composite drawin, 



Anuran. Medullary plate (ectoderm) not indicated. 



Alternate dots and dashes - endoderm Sparce stippling 



Cellular markiniis 



Heavy stippling 



notochord 



OBSERVATIONS AND DATA 



mesoderm 

 - ectoderm 



This is strictly a qualitative, olDaervational type of experiment and it will be 

 necessary to keep separate and periodic records of each stained egg or embryo. The sig- 

 nificance of the experiment will depend upon the accuracy and the completeness of the 

 record. The embryos should be kept in Standard Solution, in separate #2 Stenders, proper- 

 ly marked for identification. When the dye is moved internally, it can be traced by dis- 

 section of the living embryo. It must be remembered, however, that the dyes are soluble 

 and some will diffuse out of the embryo and also into surrounding cell areas. 



C PROSPECTIVE POTENCY D. REGION OF PRIMARY INDUCTOR 



(0RGANI2ERI 



A-proflle view of the early gastrula 

 showing the prospective areas as re- 

 vealed by the vital staining metliod. 

 B-slmllar view showing power of self- 

 differentiation of small pieces wlien 

 Isolated. C-showing prospective 

 potency (powers of differentiation 

 under various tried conditions). D- 

 showing tlie primary Inductor area; 

 stippled area, head organizer; area 

 with dashes, trunk-tall organizer. 

 After Holtfreter (193fi) . 



( From Harrl eon 191+5 : 

 Trans. Conn. Acad. Arts & Scl. 56:277) 



STACC a DOUAL ViCW 



srAcca ANTcnionview 



SrACCO. OOA&Aj.viC# 



The relative position of the pre- 

 sumptive ectodermal organ rudlmetits 

 of the head In early neurula stages 

 of Amblystoma punctatum. 



(From Carpenter 1937= 

 Jour. Exp. Zool. 75:105) 



