SEPARATION OF GROWTH AND DIFFERENTIATION 



161 



Wltschl E. 1950 - "Experimentally produced neoplasms In the frog." Proc. Soc. Exp. Biol. 

 & Med.' 2^■.k^^. 



Youngstrom K. A., I958 - "On the relationship hetween choline esterase and the develop- 

 ment of behavior in Amphihia." Jour. Neurophysiology. 1:557. 



Yung, E., 1885 - "De 1' influence des variations due milieu phy3icopchemlq.ue sur le 

 developpement des animaux." Arch, des Sci. Phyg. et. Nat. 14:502. 



Fig. 1. - 

 Fig. 2. - 



Fig. 3. - 

 Figs. 4, 5, 



Embryo embedded In the late gastrula stage exhibits, 8 days later, the 

 original egg shape but has developed stunted external organs. 



The ventral portion of an embedded neurula has grown through a hole In the 

 agar investment, while the upper portion lias not Increased In volume but 

 continued differentiating. 



The embryo has for 12 days retained the general shape existing at the time 

 of embedding. Left nasal placode and right gill region form abnormal exten- 

 sions into holes cut into the a^ar matrix. 



6. - Differential Inhibition of development in blastulae of Rana fusca 

 that have been kept for 3 days closely packed In between other eggs. The 

 frontal portion which alone had free access to the Immersion fluid Is 

 least inhibited showing a medullary liead fold and a sucker (Figs. 4-5). 

 In the absence of exogastrulatlon such eggs develop Into microcephalic 

 larvae (Fig. 6) . 



( From floltf reter, I9U5: Anat. Bee. 95:59) 



