456 



SCIENCE 



[N. S. Vol. XXVIII. No. 718 



The Cyclopean defect, as Spemann' contended, 

 is present from the first in the same condi- 

 tion that it will continue throughout de- 

 velopment. 



In mammalian cyclopean monsters the nose is 

 prevented from descending as it normally does 

 by the presence in its path of the median eye. 

 The nose is thus above the eye and shows as 

 a proboscis-like mass on the forehead. The 

 nasal pits in the fish are laterally placed above 

 the mouth and slightly antero-median of the 

 two eyes. In the cyclopean monsters the two 

 pits are generally united, though at times 

 separate, and are situated unusually far for- 

 ward and above the eye. The mouth in the 

 normal fish is anterior, the lips projecting 

 beyond the forward limits of the head. In 

 cyclopean iish the median eye occupies this 

 position and often projects forward, suggest- 

 ing a miner's lantern in the front of the head. 

 This anterior eye prevents the forward devel- 

 opment of the mouth, so that its structures 

 remain in a ventral position and hang down 

 as a proboscis-like organ, recalling in a 

 striking way the nose of the mammalian 

 Cyclops, and in fact the two are due to like 

 causes. In the mammal the nose is prevented 

 in its downward growth by the median eye, 

 while in the fish the antero-median eye pre- 

 vents the forward growth of the mouth ar- 

 rangements. 



The magnesium solutions induce the devel- 

 opment of two types of one-eyed monsters. 

 First, the true cyclocephali which may have 

 a perfectly single median eye with one optic 

 nerve, one lens and one pupil, or a median 

 eye showing more or less double nature, hav- 

 ing two optie nerves and paired retinse, or in 

 others entirely double eyes with two lenses and 

 two pupils present. A second type of monster, 

 which is new, may be termed Monstrum mon- 

 oculum asimmeiriciim; a monster with one 

 asymmetrical eye, since it has only one perfect 

 eye, which is one of the normal pair of eyes 

 occupying its typical lateral position. The 

 one eye in all cases is perfect while its mate 

 may be represented by either a small eye, a 

 mere cellular mass indicating an optic cup, 

 or again all evidence of the second optic 

 'Spemann, Zool. Jahrhvch, Supp. VII., 1904. 



cup may be wanting. This peculiar one-eyed 

 condition occurs in a great many of the em- 

 bryos in the various Mg solutions. Should 

 such a monstrosity have been caused by me- 

 chanical injury, as cutting or pricking certain 

 early brain areas, the evident conclusion would 

 have been that one of the eye anlagen had 

 been injured while the other had not. Any 

 other interpretation would have been faced 

 by the above conclusion as a criticism and it 

 would have been almost impossible to meet. 

 In the case of the Mg action it is clear that 

 such embiyos have developed one eye normally 

 while the production of the other was in some 

 way inhibited, although the anlagen of both 

 were exposed to the chemical. 



These embryos throw interesting light on the 

 development of the crystalline lens. In many 

 of them a lens forms from the ectoderm and 

 differentiates independently of the influence 

 of an optic cup. Some embryos with one 

 lateral eye and the other wanting have a per- 

 fect lens on the eyeless side. The lens lies 

 freely in mesenchymous tissue and is discon- 

 nected entirely from any portion of the cen- 

 tral nervous system. Several experimenters, 

 Lewis* and others, have held that the lens 

 during its development is in a dependent rela- 

 tionship with the optic cup and they have 

 shown that if the optic cup be removed a lens 

 fails to form. The fish embryos are against 

 the universal application of such a view. 

 Spemann° has recently found that in one spe- 

 cies of frog, Eana esculenta, the lens may 

 arise independently of the optic cup stimulus 

 and is self-differentiating. 



To conclude — experiments now show that 

 cyclopean fish embryos may be produced by 

 the action of two salts of magnesium in sea- 

 water solutions. The embryos exhibit various 

 conditions of the cyclopean defect from the 

 earliest appearance of the optic vesicles. 

 Cyclopia is not due to a subsequent union or 

 fusion of the two eye elements after their free 

 and distinct origin. 



C. R. Stockard 



Woods Hole, Mass., 

 September 3, 1908 



' Lewis, Am. Jour. Anatomy, 1904. 



" Spemann, Zool. Anzeiger, XXXI., 1907. 



