230 EDITH PINNEY 



Fundulus heterocUtus 9 X Fundulus heteroclitus cf 



^My observations on the Fundulus egg concern only the num- 

 ber and form of the chromosomes and agree in the main with 

 those of previous observers. 



The tjT)ical long thin rods are shown in figures 1 and 2. The 

 straight ranks of chromosomes in anaphase stages are more strik- 

 ing in the object itself than in the drawings. The drawings 

 show only those rods which could be brought wholly into view 

 by careful focusing. 



All of the chromosomes in such lateral views cannot be seen 

 distinctly. The reason for this will be obvious from figure 3 

 which is a polar view of an anaphase plate. Forty-five chromo- 

 somes were counted, all of which appeared in one section. 



This figure was found after many mitotic figures of the hybrid 

 eggs of the cross Ctenolabrus adspersus 9 X Fundulus hetero- 

 clitus cf had been examined. Having in mind the statement of 

 Moenkhaus that 'Tn a given anaphase all of the chromosomes 

 are of practically the same length," I tried to estimate the num- 

 ber of chromosomes characteristic of Fundulus by counting the 

 longest rods in these hybrids where the long rods are more con- 

 spicuous than in a straight fertiUzed Fundulus egg. My counts 

 varied from fourteen to sixteen. 



Therefore, the large number met with in polar views was 

 surprising, but further study of Fundulus material has shown 

 that the earlier misconception was probably due to the hitherto 

 unsuspected presence on the Fundulus spindle of shorter chro- 

 mosomes. Figure 4, which gives two sections of an early ana- 

 phase, shows this to be the case. Not all of the chromosomes 

 have divided. On some parts of the spindle they are crowded 

 together and separate chromosomes cannot be distinguished. 

 As a result of this, some elements are unusually clear and the 

 presence of shorter rods is demonstrated beyond question. Only 

 the clearest rods were drawn and all of the shorter ones lay in 

 the section and not at the surface. This excludes the possi- 

 bility of their being sections of longer rods. Figure 5 is of a 

 slightly earlier anaphase. It will be noticed that the shorter 



