STUDIES OF REPEODUOTIVE ELEMENTS: I. 11 



The eight chromgsoiiies now arrange themselves on the periphery 

 of a circle just a.s in tlie case of spermatic cells. The attractive sphere 

 and the central bodies are not, as in the testicular cells, to he observed 

 in preparations treated with sublimate-alcohol, but are very dis- 

 tinct in the cells killed with picro-acetic acid. Figs. 26-29 give the 

 eggs in these stages. Fig. 26 represents only the small part of an egg, 

 in which the spindle lies. The nuclear membrane has already dis- 

 appeared, and no trace of the germinal spot and the micronucleoli is to 

 be seen. Five of the dumb-bell- shaped chromosomes are seen in a 

 curved row from this side, and the three others can be seen, bv focussino- 

 the microscope, below these. In fig. 27 we have a polar view of such a 

 spindle, while fig. 28 givea another spindle as seen from the side. These 

 three figures are drawn from preparations treated with hot sul)limate 

 alcohol, and no trace of achromatic fibres is to be seen. Fig. 29 gives 

 the spindle in the same stage -as that of figs. 26, 27, and 28, but treated 

 with picro-acetic acid. Here we see not only the achromatic filn'es, 

 Init also a trace of the vesicular membrane quite distinctly. 



This spindle is tliat of the first polar body, and travels gradually 

 towards the surface of the eo-o- where each chromosome be^'ins to 

 divide transversely just as in the first divisi(^n of testicular cells in the 

 zone of ripening. This di\'ision gives rise to the first polar body, whicli 

 is thrown out of the egg, while this is still in the oviduct. There are 

 thus eight cliroinosoincs in the first 'polar hodij and the same nuniher in 

 the other lialf of the germinal vesicle wliicli remains ifi the egg. Tlie latter 

 begins to divide directly, but now in such a manner that four of the 

 eight chromosomes are separated of from the other four. This is the form- 

 ation of the second polar body, which thus exactly corresponds with the 

 last division of the spermatic cells, as has ])een shown by Plafner'-^^^ in 

 Aulacostoma and liv Hertu-ir/^'-^ in Ascaris ea'S's. These stao-es are re- 

 presented ])y figs. 30-35. In fig. 30 the spindle of the second polar body 



