ORIGIN OF MONSTERS 541 



of the development of the blood and Ijanph vessels in the head 

 region and the resulting lack of adequate drainage. Here, how- 

 ever, much further study is necessary. Careful anatomical in- 

 vestigations of well diagnosed cases of both forms of congenital 

 hydroceplialus in man may possibly bear out the validity of our 

 assumption. Much might be gained also from studies of the 

 blood and lymph vessels of oedematous regions in experimentally 

 deformed Fundulus embryos. 



E. THE MICROSCOPIC ANALYSIS OF SOME TERATOMATA (tHE 'SOLI- 

 TARY eye' and the 'isolated eye') 



The tendency of Fundulus eggs when treated with butyric 

 acid and acetone solutions, to give rise to partial embrj^os 

 (meroplasts) has been noted in a preceding chapter (p. 499). 

 It is obvious that a careful anatomical study of these monsters 

 is very desirable, for their internal organization often discloses 

 conditions of great ontomechanical significance. At the present 

 time, while this study is yet incomplete, it may suffice to state 

 that from microscopic examination of such embryos one gains 

 the impression that the entire embryo-forming material has 

 suffered greatly from blastolysis and that after a haphazard 

 reconstitution of the surviving, but disarranged, parts of the 

 germ the latter have developed into an embryo which is neither 

 a whole, nor a s3^nmetrical part of a whole. True anterior 

 hemiembryos, i.e. formations in which an anterior half of the 

 body (e.g. beyond the level of the pectoral fins) is present, wliile 

 the rest of the bodj' is lacking, have also been found. How- 

 ever, such cases are relatively rare. For, usually the blastolytic 

 injury, whenever it is of a high degree, affects, to a greater or 

 less extent, the whole embryo-forming substance. 



Thus, it may happen that nearly all of the embryo-forming 

 material suffers destruction and that only a very small fragment 

 of it survives, which, however, is capable of further — independent 

 — development and differentiation. 



As the most interesting cases of this category may be regarded 

 some eggs in which all that can be found on the yolk-sac (except- 

 ing some rudimentary' bloodvessels) is a fragment of tissue with 



