298 Charles R. Stockard 



Fig. II, is evident. Fig. 12 shows a common type of cyclopia 

 with the three primary brain regions separated by waist-hke con- 

 strictions. Two other variations of the narrow tubular condition 

 are found in Figs. 13 and 14. The embryos are five days old and 

 no changes of importance occur from this time until the hatching 

 period is reached, except the usual progressive development of 

 the eye structures. 



The normal embryos generally begin hatching when about 

 twelve days old, one cyclopean monster hatched at this time but 

 most such indviduals were much later than the normal in coming 

 out. A twelve day cyclopean fish is seen in dorsal view in Fig. 

 15 and ventrally in Fig. 16. The large cyclopean eye projects 

 forward and occupies the position usually taken by the mouth 

 at this time. A slight indention along its mid dorsal line suggests 

 its double nature, although the ventral view (Fig. 16) shows this 

 same eye to possess only one pupil and lens. The brain of this 

 specimen is practically normal. An embryo with the two eyes 

 intimately approximated is shown in front view in Fig. 17. The 

 eyes are joined and each looks forward in a direction slightly 

 towards the side to which it belongs. A common variety of 

 cyclopean fish is one in which the eye is unusually small and 

 occupies an extremely anterior position; Fig. 18 shows such an 

 embryo. This variety is usually unable to hatch, although a few 

 were assisted in breaking through the membrane. They swam 

 rather abnormally, owing to a twisted condition of the body. A 

 dorsal and ventral view of a cyclopean fish is shown in Plate 

 I, Figs. A and B. This indicates the striking appearance pre- 

 sented by these embryos. 



b Free-Swtmming Cyclopean Fish 



Many embryos, showing the cyclopean defect in various degrees, 

 hatched normally and were capable of swimming in a manner 

 indistinguishable from ordinary two-eyed fish. These monsters 

 gave many indications of ability to see. They went to the more 

 brilliantly lighted side of the dish with the normal ones. They 

 darted away in a normal fashion when any object was placed in 

 front of the eye, while similar objects put at equal distances from 



