Artificially Produced Cyclopean Fish 329 



continues to develop and differentiates typical fibers. Most con- 

 clusive evidence favoring the independent origin and self-differ- 

 entiation of the lens is furnished by the Fundulus embryos now 

 under consideration. 



Attention has been called repeatedly to the occurrence of lenses 

 having no connection with other optical parts. It may be well at 

 this time to summarize these cases which clearly show that in 

 Fundulus the lens may arise independently and continue its devel- 

 opment and differentiation. 



Fig. 63 illustrates the budding off of the lens from ectoderm on 

 the side of the head which lacks entirely an optic cup. Fig. 61 

 shows a lens fully differentiated though lying freely in the mesen- 

 chyme of the head. It will be recalled that this is a supernumerary 

 lens; the large and small eyes of the embryo both possess lenses. 

 An optic cup can not be responsible for this third lens. Fig. 57 

 of the incomplete diprosopus shows the fourth lens of the double 

 head entirely outside the optic cup of the third eye which possesses 

 a lens. Figs. 54 and 55 show two lenses in an embryo that pos- 

 sessed no trace of an optic cup. Fig. 53 indicates a lens in its 

 usual position but no optic cup is present. In Fig. 45 a tiny lens 

 is found in front of a cyclopean eye which possesses its own lens. 

 Many other similar illustrations could be given. 



No one could hold that this indiscriminate collection of lenses, 

 all of which are entirely isolated from any connection with optic 

 cups or other eye parts, as well as in nearly all cases from the brain 

 itself has arisen through direct stimuli derived from the optic cups. 

 It is also evident that the lens after its formation continues to self- 

 differentiate. 



It seems to me that in Fundulus the case is clearly proven that 

 lens formation does not depend upon a direct stimulus from the 

 optic cup. Such a dependence as advanced by Lewis ('04) for 

 the frog is not, therefore, of universal application, nor is the view 

 tenable that the differentiation of the lens depends upon a con- 

 tinued stimulus from the optic cup. 



