Artificially Produced Cyclopean Fish 323 



left head and one with the brain of the right. Fig. 56 is a section 

 showing the middle eye somewhat back of its center so as to bring 

 the edges of the other eyes into the figure. The middle eye is 

 more anterior in position than the two lateral ones, owing to the 

 slight obliquity of the left head. A distinct lens is shown in the 

 cup in Fig. 56. On going backwards in the series we reach a sec- 

 tion passing through the middle of the two lateral eyes and the 

 posterior end of the middle eye (Fig. 57). The section shows 

 dorsally the huge double brain and ventrally a central throat and 

 most interesting of all a fourth lens. This lens lies against the 

 outside choroid coat of the middle eye and is in just the position 

 (recognizing a displacement due to development of the middle 

 eye) to be the lens of the left eye of the right head, if such an eye 

 were present. We thus have in this double head three typical 

 eyes and the fourth represented by a free lens. It was impossible 

 to detect the clear lens in the living embryo which emphasizes 

 again the necessity of sections for a definite interpretation of the 

 conditions existing in these monsters. Conclusions drawn from 

 observations on the living eggs without the comparison of sections 

 may be incomplete. The sections further make clear the nature of 

 the circular outline shown against the middle eye of the seventy- 

 two hour embryo (Figs. 21 and 57). Comparing the figures of 

 sections and those of the whole embryos, it will be remembered 

 that the sides of the sections are transposed, since the drawings 

 of the total embryos are made from a simple microscope and the 

 sections from a compound microscope which inverts the image. 

 This incomplete diprosopus monster increases the series of eye 

 monstrosities so that it passes through the cyclopean group to 

 beyond the normal. The diagram (Fig. 58) illustrates in a simple 

 way the various conditions we have considered and emphasizes 

 the continuous nature of the series. Beginning at one end with 

 eyeless individuals, we pass gradually through a series with small 

 buried cyclopean eyes (which may be indicated in the diagram by 

 a palpebral opening, such as similar mammalian cyclops would 

 show), to the perfectly single cyclopean eye, to the double eye with 

 one lens and pupil, to the hour-glass eye with two lenses and two 

 pupils, to two independent but closely approximated eyes, next to 



