Oc 



241 



Lai 



^'^ Som 



.Som 



^^'Oc 





D 



Fig. 118 



Regulation in newt embryos deficient in or overprovided with median material. 

 At the early gastrula stage, two embryos of Triton taeniatus are cut parasagittally 

 into slightly unequal lateral halves, the cuts passing on the right of the middle line 

 in one, on the left in the other. The larger right half is then stuck on to the larger 

 left half; the smaller right half on to the smaller left half. In spite of the excess 

 and deficiency of material lying in the plane of symmetry, both embryos 

 develop with normal proportions, thus showing regulation. A, " Large " embryo. 

 B, "Small" embryo: in this case, the neural fold material was partially and 

 not completely removed in the trunk-region. C, Transverse section through A, 

 D, Transverse section through B. Oc, eye; Lab, ear- vesicle; Som, somites. 

 (From Spemann and Bautzmann, E., Arch. Entiumech. ex, 1927.) 



HEE 16 



