152 T. H. Morgan. 



recorded that he was unable to cause artificial parthenogenesis In 

 Ciona intestlnalls at Naples by any of the ordinary means that 

 excite this development in other eggs. 



I shall discuss later the view as to whether eggs may be entered 

 by the sperm of the same individual, but fail to develop unless 

 incited to do so by some external agent. 



It has been pointed out in the preceding pages that the eggs of 

 Ciona may be fertilized after they have been in sea-water several 

 hours. I made a test of this again in the following experiment: 



Experiment XVII. Some eggs were cross-fertilized at once, 

 others after 30, 80, 125 minutes, with fresh sperm from the same 

 Individual. All the eggs developed. A striking fact was ob- 

 served in this case. The eggs fertilized late began to segment 

 after a shorter interval than did those fertilized at once, so that at 

 the 32-cell stage those fertilized last were only one division behind 

 the first set, and no doubt soon caught up. It appears that a 

 ripening process goes on in the egg as it stands in the sea-water, 

 so that it begins to segment more quickly after it is fertilized 

 than does an egg fertilized as soon as removed from the oviducts. 

 It even appeared that after the first cleavage the rhythm of divi- 

 sion was quicker in the eggs whose fertilization had been de- 

 layed, but this point needs a special examination which I have not 

 yet made. The discovery is all the more significant because the 

 first polar spindle Is already formed in Ciona while the egg is in 

 the oviduct, and the spindle remains resting in the equatorial plate 

 stage until the egg is fertilized; hence the difference In time of 

 segmentation can not be accounted for by the time required for 

 the breaking down of the egg-nucleus and for the formation of 

 the polar spindle after the egg has been removed from the ani- 

 mal. Some change must take place In the sea-water, which, while 

 it does not cause the polar spindle to pursue Its development, yet 

 causes the developments that take place after the spermatozoon 

 enters to go on more rapidly. 



EXPERIMENTS WITH CYNTHIA 



The ovaries of Cynthia extend far forward, and have a very 

 short oviduct. Each ovary — there appear to be two in each In- 



