POSITION OF OPTIC ANLAGE IN AMBLYSTOMA 269 



The present writer's opinion of the cause of cyclopia, which 

 was advanced in 1909, was to the effect that this deformity is 

 the result of a weakened development. Spemann has termed 

 this view the 'laming: hypothesis,' since my assumption was that 

 the A^arious chemical substances employed in producing Cyclo- 

 pean defects in fish embryos have a tendency to lower the de- 

 velopmental energies and so reduce the power necessary to ac- 

 complish the processes involved in the outpushing of the optic 

 vesicles from the brain. 



Considering the probable manner in which the cyclopean defect 

 occurs, Adami ('08, p. 241) has theoretically concluded that it 

 is due to developmental arrest or lack of vigor. While I am 

 unable to agree with the details in Adami 's argument of a pri- 

 mary growth point at the anterior tip from which is budded off 

 successively the paired parts of the two sides, the anterior ones 

 necessarily arising last after the other parts had been left in 

 more posterior positions, the final conclusion that a weakening 

 of particular developmental processes results in cyclopia is con- 

 firmed by all my experiments. 



The different . types or degrees of the cyclopean defect depend 

 upon the stage in development at which the arrests occur as 

 well as upon the strength or severity of the treatment employed. 

 I shall now attempt to defend this position with the evidence 

 at hand, and in so doing shall as decidedly prove the mistake 

 in considering the defects as the result of any failure to arise of 

 median medullary tissue (other than future eye tissue) and the 

 subsequent fusion of the lateral optic anlagen. There is no med- 

 ian tissue between the eye anlagen. The median tissue is the 

 eye anlage itself and will subsequently go to form some portion 

 of the eye, either optic cup or optic stalk, depending largely 

 upon its position and the extent of normal development attained. 



The writer had ('07, '09, '10) recorded a number of eye con- 

 ditions which are considered to be different degrees of cyclopia 

 using the term in a general sense. At any rate, these several 

 conditions differ only in degree and grade perfectly into a con- 

 tinuous series. There is no qualitative difference between them. 

 Spemann has objected to including among these defects certain 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 15, NO. 3 



