ArtificiaUy Produced Cyclopean Fish 287 



sters were double-headed with one or both heads showing the 

 Cyclopean defect and were not of the usual single cyclopean 

 type found in man and other mammals. 



Two years ago (1907) I carried out experiments in which I was 

 able to produce typical single cyclopean fish. This was the first 

 record of the occurrence of cyclopia among fishes. It is also 

 the first case of consistently producing vertebrate monsters such 

 as are known in nature by changing the chemical environment 

 in which the eggs develop. These embryos are in main details 

 similar to the mammalian cyclops, having a single median eye 

 and anteriorly placed double nasal pits. 



The monsters were produced by allowing the eggs to develop in 

 sea-water in which there was an excess of MgCla- Cyclopia 

 occurred in a large percentage (at times 50 per cent) of the 

 embryos. The discovery was made so late in the spawning 

 season that it was impossible to investigate the details of the 

 cyclopean defect or rear the embryos to hatching in order to 

 observe their ability to swim or to see. The method of produc- 

 tion, however, off'ered such an exceptional opportunity to obtain 

 abundant material for studying all stages of development and 

 degrees of cyclopia that this more extended survey was under- 

 taken. 



The following account includes a comparative study of cyclopean 

 embryos from the earliest appearance of the optic vesicle to the 

 perfectly formed free-swimming fish with a functional cyclopean 

 eye. 



The experiments were conducted in the Marine Biological 

 Laboratory at Woods Holl, Mass., during the past summer, while 

 occupying one of the rooms of the Wistar Institute. 



MATERIAL AND METHOD. 



As in my previous experiments, the eggs used were those of the 

 teleost fish, Fundulus heteroclitus. 



The method of producing the defect was much the same as that 

 previously employed although expanded and modified in many 

 ways. During the early part of the season it was difficult to find 



