112 GEORGE O. SHINJI. 



wing-developing substances correspond with the former, and the 

 non-wing-developing substances to the latter. Further, so far 

 as these non-wing-developing substances are concerned, Herbst 

 (1906), Loeb (1907), and others have proven them to be in- 

 jurious to other classes of animals. For example, Herbst (1906) 

 found that the addition of potassium salts to sea water sup- 

 pressed the development of the arms of the Echinus larvae. 

 These investigators have also found that the development of the 

 alimentary canal of the Echinus larva was impossible in mag- 

 nesium-free sea water. Again, Fischer (1903) and others have 

 proven that magnesium salts counteract the effect of saline pur- 

 gative. All these results obtained with other animals by various 

 investigators suggest that wing-developing and non-wing-develop- 

 ing substances exert, respectively, characteristic action on the 

 organic matter. We have at least two evidences that tend to 

 show that in all probability the two phenomena of the appearance 

 of the winged or wingless individuals may be due to the physi- 

 ological actions osmosis and surface tension. One of these is the 

 presence of more of the fat cells, which are derived from meso- 

 derm cells, in the apterous forms than in the alate forms, and the 

 other is the fact that the cells of the apterous forms are slightly 

 larger than those of the alate forms. The first of these evi- 

 dences suggests the probable degeneration of muscle and probably 

 nerve cells at the time when the wing cells are in the process of 

 differentiation. The degeneration may, it must be said, be due 

 to the increase in the cytoplasmic area of the cell and the sub- 

 sequent loss of the coordination between the nucleus and its 

 surrounding cytoplasm, as is manifested in the case of the fat 

 body. The difference in the size of the two forms may not only 

 strengthen the view just presented, but also explains why the 

 winged forms resemble the male, and the apterous, the sexual 

 females; for the two winged forms, the male and the alate vivip- 

 arous females are much more highly developed than the two 

 wingless sisters, and are produced by the same factor the 

 decrease in surface tension and osmosis. These physiological 

 factors osmosis and surface tension produce the male if they act 

 on the egg at the time of polar-body formation, and the winged 

 viviparous female if they act on the larva within three days after 

 birth. 



