CYCLOPIA COMPARISON AND RECORDS 43 



accompanies fusion of mid-brain structures has been mentioned above in connection with the 

 brain. 



Skeleton. The trabeculae cranii appear as a single bar of cartilage underlying the median 

 eye. Either they formed a single structure from the first, and this seems to me most probable, 

 or their fusion was remarkably early and complete. Olfactory capsular cartilages may be present 

 or absent ; when present, they are developed in connection with the anterior ends of the supra- 

 orbital bars. The palato-quadrate, the mandibular, and the hyoid bars tend to be shortened, in 

 correspondence with the general transverse narrowing of the mouth-parts. 



Comparison with Cyclopia in Mammals. 1. While olfactory nerves are not found in the typical 

 mammalian cyclops, they are present in all my trout specimens, being traceable from the fore-brain 

 to the small olfactory pits on the under surface of the frontal process. If, as seems certain, this 

 process represents the " proboscis " of a cyclopic mammal, the " proboscis " in question can have no 

 relation with parts of the brain behind the cerebral lobes, and, in particular, none with the 

 hypophysis. 



2. Dropsy of the central cavity of the brain or of the space between brain and skull is not 

 characteristic of cyclopia in fishes. This may be contrasted with the usually dropsical condition of 

 the hemispheres and the meninges in cyclopic mammals. 



3. The relatively good development of all parts of the brain, particularly in type A among 

 fishes, is remarkable. Indeed, there seems to be no absolute bar to prevent a specimen of this kind 

 from surviving and obtaining food for itself as in the remarkable case recorded by Paolucci. 



Other Records in Fishes. The literature of cyclopia in fishes is by no means extensive. Small 

 as it is, however, it provides two most interesting facts. One has reference to the growth and 

 survival of a cyclopic fish, and the other to an agent in the production of cyclopia, which seems 

 almost specific in its action. 



Lereboullet (143) figures a pike embryo with a cyclopic eye which is furnished with a single 

 lens, and has probably arisen by the fusion at an early stage of two separate eye rudiments. 

 Girdwoyn (81) also figures a typical cyclopic salmonid embryo well advanced in development, and 

 resembling the specimen I have illustrated in PI. XXIV. fig. 100. 



The remarkable instance of survival referred to above was recorded by Paolucci (181). The 

 specimen, caught in the Adriatic not far from shore, and placed in the Natural History Collection of 

 the Technical Institute at Ancona, was identified by F. Paolucci as probably belonging to the species 

 Myliobatis noctula Dum., though it presented certain characters intermediate between this species 

 and Myliobatis aquila. The dimensions, as judged from the author's illustrations, are : length of 

 head and body, not including the tail, 9 \ inches ; breadth between tips of pectoral fins 1 7 inches. 

 There is a single very large median eye, set in the place of what should be the fleshy anterior 

 border of the head. This border is divided into two parts sticking out like horns, " 3 cm. long, 

 and as thick as a finger," one on either side of the eye. The nostrils and the fleshy upper lip 

 are both awanting. The above record, regarding the authenticity of which there seems not the 

 slightest reason to express doubt, is probably the only one which indicates that any vertebrate 

 animal has ever been found in actual adult life embodying the fabled Cyclops type. 



A very interesting set of experiments has been carried out by Stockard (337) on the 

 production of cyclopia in the eggs of Fundulus heteroditus by the addition of magnesium 

 chloride to the sea-water in which the eggs were being hatched. With certain strengths 

 of solutions (i m. sea-water solutions of MgCl 2 ), one-eyed embryos occurred with surprising 

 regularity in 50% of the eggs. The remaining embryos in these solutions were apparently 

 normal so far as the eyes were concerned. The structure of the compound eye corresponded 

 almost exactly with that described above under cyclopia (A). Stockard does not give 

 particulars regarding the brain, but from his figures, particularly Figs. 4-5 p. 253, it may 

 be inferred that some degree of fusion existed in the region of the cerebral lobes and the third 

 ventricle. As regards the coming together of the two eyes, Stockard considered it to be through an 

 antero-medio-ventral fusion of the elements of the two optic vesicles at an early developmental 



