304 Charles R. Stockard 



interesting to know whether the "cyclopean mouth" is functional. 

 The mouth does not possess a wide opening as it would normally 

 although a small aperture is sometimes distinguishable near the 

 end of the proboscis. No attempt was made to feed the embryos. 



c Living Monstra Monophthalmica Asynunetrica 



These asymmetrical one-eyed monsters may also be identified 

 in early stages of their development. They have a single eye 

 situated on one side of the head. Such an eye appears in some 

 cases as though it were cyclopean and one might easily imagine 

 the cyclopean eye becoming displaced from its usual median 

 position to one side or the other of the head. Studying such eyes 

 in section, however, clearly shows their single unmated origin and 

 condition. An embryo of this kind is shown when five days old 

 in Fig. 19. The brain is slightly abnormal and the pigmentation 

 scarce for such a stage of development. The eye occupies the 

 usual place of the paired eye of that side. A twelve day embryo 

 shortly before hatching is illustrated by Fig. 20. The shape of 

 the body and of the head is comparatively normal. The unpaired 

 eye is slightly forward of its usual position. 



Many of these embryos hatched. A few of them swam in 

 circles, often whirling around with great rapidity, much as Japan- 

 ese waltzing mice do. Others swam in irregular spirals and only 

 progressed in a straight direction with difficulty. This peculiar 

 one-sided manner of swimming is not due to asymmetrical vision, 

 but results from a defective muscular arrangement, the animal's 

 body being slightly bent or twisted so that it is unable to straighten 

 perfectly. Some embryos with this eye on one side had normally 

 straight bodies and these were capable of swimming in a direct 

 course with apparently as much ease as a two-eyed fish or the 

 symmetrical cyclopean embryos. 



These monsters also lived, free-swimming, for some time. In 

 a few cases their mouths were perfect, but in others the mouth 

 parts were distorted or twisted by an asymmetrical condition of 

 the ventral head region. 



