192 J. S. NICHOLAS 



Harrison ('45) bases the polarity of the egg upon three factors: the 

 dipole character of protein molecules and their resultant orientation, 

 regional gradational dififerences in the composition of dipole molecules, 

 and regional differences due to cytoplasmic inclusion. Schrodinger 

 ('45) postulates an aperiodic crystal to account for some of the situa- 

 tions which occur in living systems. Needham ('42) invokes a para- 

 crystalline state or a liquid crystal, but this state would have to be a 

 relatively late one, probably occurring in the early neurula. 



The question of gradients within the egg and the effects of different 

 things upon them has long been subject to much speculation. In a recent 

 article Child ('46) discusses the Spemann organizer concept in rela- 

 tion to the various gradient systems. The results are suggestive but not 

 conclusive. The experimental data concerning the Spemann organizer 

 is confined entirely to the amphibian embryo. Child points out that the 

 primary organizer is not primary, since it does not determine external 

 or other axiate patterns in natural development. He bases this idea on 

 Holtfreter's ('44a) and Earth's ('41) work on neuralization without 

 organizer action. He neglects to point out the fact that the amphibiolo- 

 gists themselves early deserted the idea of the Spemann organizer as 

 the only single factor responsible for all organization. While it is ex- 

 ceedingly important in nervous system formation, there are other fac- 

 tors which come into play, some of which have been set in motion far 

 earlier than the Spemann organizer, which cause the movements and 

 reactions of certain parts of the egg. Child has intentionally focused his 

 attention upon the later stages of development in the amphibian and 

 has not mentioned the work which deals with earlier organization 

 patterns. 



This is particularly true as we look back and survey some of the 

 literature which has to do with the organization complex in fishes. 

 Morgan in 1893 reported that the yolk might be removed from the egg 

 of Fundulus and that the embryo would still continue to form. Oppen- 

 heimer ('36a) has shown that the blastomeres may be removed from 

 Fundulus eggs and that if not removed too early in development the 

 disc will gastrulate and will develop embryonic structures or even com- 

 plete embryos. Tung, Chang, and Tung ('45) have confirmed these 

 results upon the eggs of goldfish, Carassius auratus. Fragments con- 

 taining the blastodisc but less than half the yolk formed hyperblastulae. 

 Fragments of the same size derived from 4-cell stages formed embryos. 

 After the 8-cell stage the isolated blastodisc formed embryonic struc- 

 tures or embryos. Oppenheimer ('34, '36b) postulated that some sub- 



