REPRODUCTION IN THE INFUSORIA. 



193 



the principal variations as to size aucl number which the eggs 

 present : 



'' Usually the number of eggs which divide at once in- 

 crease in an inverse ratio to the number of eggs already 

 formedj and to their degree of maturity, while the time re- 

 quired for a given egg to divide_, increases directly with the 

 same conditions. It would seem that the eggs placed to- 

 wards the ends of the chain divide more frequently than those 

 which occupy an intermediate position. Their multiplication 

 does not completely cease until the moment of sexual union, 

 and just up to this period, that is to say, at all times, we 

 meet with individuals in which one or two of these, often a 

 much greater number, present more or less advanced traces 

 of division." 



As a general rule, if two Infusoria of about equal size be 

 compared, the eggs (as might be expected) are largest when 

 least numerous. 



In the Vorticellina, and some other forms [Prorodon 

 niveus, Bursaria truncatella, Trachelius ovum, &c.), each di- 

 ■vision of the internal vesicle, or its parts, is not immediately 

 followed by that of the other contents, so that the vesicles 

 appear by themselves in the axis of tlie ovary, the granular 

 substance of which lies between them and the external mem- 



