556 E. I. WERBER 



while not sufficiently great to cause a rupture of the two halves 

 of the primordium, has only shifted one of them out of its normal 

 position on the yolk. Briefly, it may be said, that the effect of 

 blastolysis, due to chemical alteration combined with osmotic 

 pressure, was in this case a highly deformed amorphous embryo, 

 which as figure 44 shows, can in toto easily be mistaken for 

 coalesced m^alformed twins. 



To blastolysis by chemical alteration and increased osmotic 

 pressure are evidently due also the conditions found in the 

 following embryo now to be described. 



As can be seen from figure 30 the embryo is very deformed 

 and only slightly suggests the body form of a fish. The irregu- 

 larity of form pertains particularly to the head and the trunk, 

 which latter appears to be greatly distended. There is no clear 

 indication of the true nature of the embryo, namely that it is, 

 as examination of sections shows, a case of a partial, fused 

 dupHcity. 



The most anterior (transverse) sections show an anophthalmic 

 and sharply pointed, highly oedematous head. Between the 

 head and the yolk-sac there is a space filled with plasma (fig. 85) 

 which can be recognized as the enlarged, oedematous pericardial 

 vesicle. A lens is seen situated laterally, but there is no trace 

 of an optic cup. Practically at the same level with the lens 

 there appears ventro-laterally to it a transversely sectioned tube- 

 like structure (gut?) which can be followed only in eight sec- 

 tions of 7ju thickness. Following the sections posteriorwards 

 the oedematous brain is seen to increase in size and to be highly 

 deformed. Still more posteriorly, i.e. at the posterior level of 

 the lens the brain mass makes the impression of two fused, 

 malformed brains, there being between the components a distinct 

 lamella. 



In sections through this double brain mass there can be seen 

 at a distance from the embryo a transversely cut fragment of 

 nervous tissue which makes the impression of a deformed spinal 

 cord. It corresponds to the tissue fragment (tf.,) in figure 30. 

 Between this fragment, the embryo and the yolk, there is a 

 cavity filled with a plasma-like mass (fig. 86). 



