ORIGIN OF MONSTERS 543 



Of the other tissue fragments, which have been observed in 

 the Uving egg, as well as after fixation, one has proved to be 

 another solitaiy eye. This other eye is also seen to arise from 

 nervous tissue, which, obviously, is a (very defective) brain 

 (fig. 56). The retina of this second sohtary eye is in a very 

 mdimentary stage of differentiation, no pigment layer is present, 

 nor an iris; the cornea is very poorly differentiated, while the 

 lens is practically perfect. This second eye is much smaller 

 than the first one described, from which it is 262^ distant. 



These microscopic findings are very significant for the analysis 

 of the morphogenesis of the sohtary eyes of this egg. Since no 

 embryo can be found in the egg, it is obvious that with, the 

 exception of very small fragments all of the earhest embryonic 

 primordium has suffered destruction. It is likewdse ob^dous 

 from the great distance between the sur\dving fragments which 

 have given rise to solitary eyes that they have secondarily been 

 shifted to distant parts of the yolk. The destruction of the 

 embryonic anlage is possibly in the nature of a blastolytic disin- 

 tegration (chemical blastolysis), while the apparent dispersion of 

 its small surviving remnants would seem to be due to an in- 

 crease in the eggs internal osmotic (exosmotic) pressure (osmotic 

 blastolysis) . 



That both chemical (toxic) and osmotic blastolysis underlie 

 the origin of such meroplastic formations is indicated by the 

 next case of 'solitaiy eye' now to be described. 



On examination in toto (fig. 40) of the transparent egg (both 

 while hving and after preservation) no embryo could be seen 

 anywhere. All that could be found on the yolk was a small 

 meroplast, which made the impression of a ver\^ large eye with 

 a protruding, unproportionally large lens. 



The true conditions obtaining in this meroplast, however, are 

 somewhat different. For, examination of sections proves unmis- 

 takably that this meroplastic formation presents a case of soli- 

 tary synophthalmia. 



In the first three sections (fig. 57) there appears the lens of 

 one of the eye components (left). It is perfectly well developed 

 and surrounded by an epithelial capsule. On one side of the 

 cross-sectioned lens is seen a thickened mass of tissue which 



