Artificially Produced Cyclopean Fish 295 



the Cyclopean condition existed as such from the first appearance 

 of the optic vesicles, and no subsequent fusion of the two optic 

 vesicles or cups took place after that time. 



A forty-two hour embryo is shown in Fig. 3. It is seen to be 

 well formed and the optic vesicles are clearly outlined on either 

 side of the head. Fig. 4 illustrates a cyclopean individual of the 

 same age. The single optic vesicle occupying a ventro-median 

 position is shown through the transparent embryo. This young 

 individual with its newly formed optic vesicle shows a typical cyclo- 

 pean condition, and no indication is seen of two separate elements 

 that would later fuse. Other embryos at this age have abnormally 

 twisted cephalic regions and show no indication of eyes, although 

 the cyclopean eye might easily be concealed by the bent brain 

 (Fig. 5). Such embryos at later periods are found to be cyclopean 

 and to have narrow tubular brains showing more or less abnormal 

 bendings. 



When the embryos are about three days old, the brain has 

 expanded and presents a distinctly bilateral appearance; the 

 optic cups are well developed and the lenses are partially formed 

 (Fig. 6). A Cyclops monster at this time has a well formed body 

 and the brain is often normal, though in Fig. 7 it is inclined toward 

 the narrow tubular condition and is anteriorly twisted. The ven- 

 tromedian eye is clearly seen through the brain and the outline of 

 its lens is distinct. A somewhat younger, sixty-five hour, embryo 

 is shown in Fig. 8 with a superficially perfect brain and two optic 

 cups intimately approximated. The telencephalon is seen to 

 protrude beyond the eyes, as is the case in the normal individual 

 (Fig. 6). 



Three four-day embryos are shown by Figs. 9, 10 and 11. The 

 brain and spinal cord at this time are clearly mapped out by a 

 coarse pigmentation, the two hemisphere-like portions (corpora 

 bigemina) of the mid-brain are distinctly formed and the eyes are 

 large with the lens clearly outlined within the cup. A cyclopean 

 monster with a perfectly formed large ventro-median eye is 

 illustrated by Fig. 10. Comparing its brain and other parts with 

 the normal (Fig. 9), one fails to find any important deviations. 

 The abnormal condition of the narrow tubular brained cyclops, 



