ORIGIN OF MONSTERS 557 



A second tissue fragment ((fo of figure 30) can be seen in more 

 posterior sections on the side of the yolk opposite the embryo. 

 This fragment proves on careful examination to be a very rudi- 

 mentary eye, of which only the lens can be recognized with 

 certainty. 



The larger one of the two brain components (a) is more oede- 

 matous and its staining reaction with haematoxylin is weaker 

 than that of the other component (b). This fusion of two brains 

 into one ma;ss becomes very distinct in still more posterior sec- 

 tions where component a now gradually diminishes in size, until 

 it entirely disappears from view while the component b has 

 encroached upon its place in the section. Several sections further 

 posteriorly (fig. 86) there is seen a large optic cup at the 

 ventral part of the brain component b. Retinal cells (rods and 

 cones) of this optic cup can be recognized in some sections. 

 The following is the complete picture presented at this level. 

 Almost half of the section through the embryo is taken up by 

 brain component b. Laterally from it is seen a transversely cut 

 notochord, while ventral to it is the optic cup, and ventrally 

 from the latter are seen cross-sectioned coils of an intestine. 

 In the intestines a fibrin-like mass can be noticed, which points 

 to defects in the circulatory system. Following the series more 

 posteriorly there can be seen gradually to appear the spinal cord 

 above the notochord. It is at first on one side fused with brain 

 component b while in sections at a more posterior level (fig. 

 87) it is separated from the latter by a mass of mesodermal 

 cells (poorly differentiated myotomes?). In still further sections 

 the brain component b disappears entirely while a large cavity 

 lined with endothelial cells and filled with plasma is seen to 

 follow it in the sections. The last sections are cross sections 

 of a deformed tail. 



At the outset of the description of this monster it has been 

 stated that the conditions found on microscopic examination 

 point to blastolysis as a factor underlying its formation. While 

 of course, a complete analysis of the morphogenesis of this 

 monster is practically impossible, the two extra-embryonic tissue 

 fragments would seem to point decidedly to blastolytic action. 

 Considerable difficulty, however, is presented by the interpre- 



