THE BIOLOGY OF THE CELL SURFACE 



doubtless true of other substances that enter cells: they 

 react first with the cytoplasm. 



Experimental cell-study gives instances of aberrant 

 behavior of the chromosomes in egg cells. All of this work 

 Indicates that the experimental means first affects the 

 ectoplasm. According to the theory here advanced this 

 ectoplasmic effect Is responsible for secondary effects on 

 the whole egg cell. Among these Is the aberrant behavior 

 of the chromosomes. 



In the early days of the modern work on genetics, the 

 experimental analysis could not have got very far without 

 the descriptive studies on the behavior of the chromosomes. 

 In the first line of this classic period for cytology stands 

 Boveri's work. According to his analysis of experiments 

 on dispermic fertilization, normal development depends not 

 on the number but on the proper combination of chromo- 

 somes. These experiments furnished part of the basis for 

 the theory of the individuality of chromosomes. 



To secure dispermic or polyspermic fertilization of an 

 echinid egg, one must first weaken its ectoplasm or employ 

 heavy insemination. Where polyspermy ensues without 

 experimental weakening of the eggs, we must assume that 

 they were weak at the outset. The aberrant development 

 of the blastomeres in his experiments Boveri related to the 

 wrong combinations of chromosomes. But these combina- 

 tions themselves depend upon the weakened conditions 

 in the cytoplasm which make dispermy possible. In the 

 normal egg the unimpaired ectoplasm protects against dis- 

 order of the chromosomes. 



Aberrant behavior of paternal chromosomes Is revealed 

 In cross-fertilized echinid eggs when in certain crosses the 

 paternal chromosomes, failing to take part in the mitotic 

 process, are eliminated from the spindle. The possibility 

 for cross-fertilization in all these cases is rendered greater 

 by Injuring the ectoplasm of the eggs. Here again, there- 



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