attthor's abstract of this paper issued 

 by the bibliographic service, april 17 



THE INITIAL BLOCK TO NORMAL DEVELOPMENT 

 IN CROSS-FERTILIZED EGGS 



I. CROSSES WITH THE EGG OF FUNDULUS 



II. RECIPROCAL CROSSES BETWEEN CTENOLABRUS AND PRIONOTUS 



EDITH PINNEY 

 Lake Erie College 



SEVENTEEN FIGURES (tWO PLATES ) 



There is a marked absence of specific fertilization qualities 

 among the germ cells of teleosts, such as has been demonstrated 

 in the eggs of certain invertebrates. It is true that the per cent 

 of fertihzed eggs in fish hybridization varies widely, both in dif- 

 ferent crosses and in the same crosses at different times, but no 

 quantitative study of this variation has been made. There is, 

 however, a specificity factor present in fish eggs which has been 

 met with in the eggs of echinoderms (9). It expresses itself in a 

 disturbance of the mitotic process during the first cleavage 

 anaphase and fornjs the first critical block to development. 

 All of the nuclear phenomena following fertihzation up to the 

 time that the equatorial plate is formed in preparation for the 

 first cleavage are normal in all of their visible morphological 

 aspects. During the anaphase, however, abnormahties arise. 



In an earlier paper (15) it was shown that the abnormalities 

 in development in certain crosses could be traced to these abnor- 

 malities in the mitosis of early cleavage. Two general types of 

 mitotic behavior during the first cleavage division were observed 

 and described; one type being normal, division of the chromatin 

 occurring with undisturbed mitotic precision; the other type 

 being abnormal, showing a number of irregularities in the accurate 

 division of the chromosomes, such as unequal distribution, 

 fragmentation, and, possibly, elimination. That this early 



401 



