146 CARL RICHARD MOORE. 



gradual increase in the number of cleavages. But development 

 after this length of butyric acid exposure is not preceded by 

 membrane production. 1 From an exposure of one minute the 

 percentage of cleavages continues to rise as the length of exposuie 

 is increased, until the greatest number of cleavages is obtained 

 after an acid exposure of approximately two minutes (varying 

 with different lots of eggs). From this length of exposure to 

 longer ones the possibility of fertilization gradually decreases 

 until exposures from five to ten minutes to the given strength of 

 butyric acid absolutely prevents fertilization of the eggs. 



It is of significance that the majority of eggs fertilized after a 

 prolonged butyric acid treatment cleave very irregularly when 

 cleavage is present at all. Cleavage many times is delayed, 

 cells appear very unequal in mass, the usual radial type of normal 

 cleavage is lost and the pattern becomes very obscure; nuclear 

 division may appear when no evidence of cytoplasmic cleavage 

 is present. 



Likewise the larvae that result from eggs over exposed to 

 butyric acid are very abnormal. Usually they are slightly 

 retarded in their development as compared with a similar stage 

 of differentiation in a normal series. The degree of abnormality 

 in such lots is extremely variable. Many of the eggs do not 

 cleave at all ; some go to 2, 4, 8, 16 cells or farther and disintegrate. 

 Most of the larvae do not swim at the surface of the water but 

 remain on or near the bottom of the dish. Almost any foim 

 from a rounded mass of protoplasm barely exhibiting a slight 

 quivering or very slow spinning movements up to normal indi- 

 viduals may be observed. Forms having only one appendage 

 representing an arm or others with extremely long arms very 

 closely bound together, arms widely separated even to 180- 

 large oral lobes, scarcely visible oral lobes, or very irregular 

 masses of protoplasm with blunt projections, were noted. The 

 rate of mortality was usually very high in these abnormal lots. 

 With an exposure approximating the point at which no fertiliza- 

 tion is possible, no normal larvae were obtained; irregular masses 

 of protoplasm scarcely resembling a normal larva were the only 



1 Herbst, '06, has called attention to the fact that eggs over-exposed to butyric 

 acid do not produce membranes when inseminated with sperm. 



