500 MONTGOMERY. [Vol. XV. 



forty ; and in Piscicola, usually one in the ovum and the 

 ganglion cells, about twelve in the mature muscle cells, and 

 three hundred or four hundred in the subcuticular gland cells. 

 From the data at hand we accordingly conclude that the 

 number of nucleoli is not constant for the species. (On the 

 number of nucleoli at different stages in amphibian ova, cf. Car- 

 ney and Lebrun, '97a). 



In order, to determine whether the number of nucleoli in ^g'g 

 cells were fixed for, or in any way determined by, the particular 

 groups of Metazoa, I have compiled the following tables (pp. 501- 

 505) for the larger groups, these tables representing the data 

 of previous investigators and of my own observations. In them 

 four classes of germinal vesicles are distinguished according to 

 differences in the number and kind of the nucleoli ; this classifi- 

 cation is only for convenience' sake, only arbitrarily chosen, and 

 is probably not a natural one. On the left hand is given the 

 name of the genus or group ; the asterisk corresponding to each 

 form indicates by its position in a particular vertical column the 

 nucleolar relations of the ovum of the form specified ; and next 

 to the asterisk is placed the name of the authority. In some 

 cases two investigators may have reached different conclusions 

 in regard to the nucleolar relations, so that for these cases two 

 asterisks were employed. 



One must be extremely cautious in any attempt to draw 

 •conclusions from these data, not only because the data are 

 so meager, but also because where data have been culled 

 from so many different observers some of the facts may ulti- 

 mately prove to have been erroneous. Thus many of these 

 ova may have been examined at only one point in their develop- 

 ment, and in others paranucleoli may have been entirely over- 

 looked, or may have been confused with true nucleoli. But 

 taking this mass of observations as it stands, the following gen- 

 eral conclusions may be drawn : we find that a large number of 

 nucleoli is not always characteristic of ova with a considerable 

 amount of deutoplasmic substances, for a single nucleolus is 

 typical for the birds and for many of the Arthropoda. Further, 

 the number of the nucleoli does not seem to be dependent 

 upon the amount of yolk, nor upon the mode of cleavage. 



