Munson, Organization and Polarity of Protoplasm. 377 



Evidences of Persistence of Centrosome 

 and Aster. The discovery of the centrosome and aster in the 

 fertilized egg of Ascaris aroused high hopes that we had finally found 

 some positive evidence of protoplasmic structure, more particu- 

 larly an orderly arrangement of parts of the cytoplasm, which 

 seemed to offer some basis for a morphological explanation of 

 heredity and natural selection. These high hopes, however, seem 

 to have been needlessly shattered by the seeming disappearance 

 of the aster and centrosome belonging either to the egg or to 

 the sperm. As a result, too, of Weismann's theory, which 

 locates hereditary qualities in the nucleus, cytoplasmic structure 

 which might form a basis for heredity has been denied. The 

 prominent aster and centrosome, so easily seen in leucocytes, 

 have also been described as temporary, dynamic centers arising 

 from the movement s of these cells. These are all inferences based 

 on negative evidences. Such evidences can easily be obtained by 

 bad methods. One investigator of the egg of Limulus — to give 

 one instance — has stated that there is nothing in the egg of 

 Limulus corresponding to the yolk-nucleus (vitelline body) in the 

 egg of Spiders, a statement which I have shown to be untrue 1 ). 



In the very youngest eggs of Limulus, to be seen only in 

 young Limuli a few inches long, when the eggs enter on the period 

 of growth, after multiplication of the oogonia, the centrosome 

 is to be found, in the midst of archoplasm, which is clearly a con^- 

 tinuation of the centrosome and aster of the .oogonia (fig. 19, 

 pl. Ia). It forms a crescent-shaped body partly enclosing the 

 nucleus, and with Lithium carmine and Lyons Blue can be diffe- 

 rentiated as a blue body from all other parts of the egg. This 

 same body can be traced in larger animals, after two or three 

 years of growth, up to the adult Limulus with ovaries filled with 

 mature eggs. In the smaller eggs, the body may still retain the 

 crescent form, but more often, when the amorphous metaplasm 

 is limited, it Stands out clearly as a distinct aster (fig. 20, pl. Ib). 

 In my work on Limulus, I have given a füll account of this cen- 

 trosome and aster. Space will not permit a description here of 

 additional observations which I have made. I invite an inspec- 

 tion of figs 19, 20, 22, 23, 24, pl. Ib, 25, pl. Ib. The microscopic 

 preparations from which my drawings are made are now on ex- 

 hibition at this Congress. 



Special attention may be called to figs. 20, 22 and 23. Who 

 will venture to say that the astral formation in these ovarian 

 eggs are not, in nature, similar to the aster in the fertilized egg 

 of Ascaris, fig. 15, and in the first two cleavage cells of the same 

 ;, fig. 16. And are they not also identical with aster and cen- 



l ) Munson: The Ovarian Egg of Limulus, a contribution to the problem 

 the of centrosome and yolk-nucleus. (Journal of Morphology, Vol. XV, No. 2, 1898.) 



