EXPERIMENTS ON EGGS OF CH^TOPTERUS. 143 



record the individual experiments, I will state the precautions 

 against error that were used : 



The majority of the Cliatoptents females were gathered by me, 

 or under my direct supervision, and were never placed in the 

 same vessel with males. Each female was washed in a stream 

 of fresh water before eggs were removed from it. Except dur- 

 ing two days no males were allowed in the same laboratory with 

 the females. One check of eggs in sea-water and another in sea- 

 water to which KC1 had been added, were kept to each experi- 

 ment. None in the check in plain sea-water developed, while 

 many in the KC1 sea-water developed cilia. In each lot of eggs 

 the operations were continued from the first appearance of the 

 first polar body to the formation of the second polar body, and 

 sometimes a few minutes later. Some eggs were fixed and sec- 

 tioned immediately after the operation, others at later intervals up 

 to twenty-four hours, and in this way was determined whether 

 any chromatin had been left in the egg. 



EXPERIMENTS ON THE EGGS OF ASTERIAS FORBESII. 



Eggs from which the chromosomes were removed and eggs 

 from which the whole nucleus was removed were fertilized with 

 sperm of the same species. These operated eggs did not show 

 any differences from the normal save in number of chromosomes, 

 in increased tendency toward polyspermy and in increased mor- 

 tality. This last prevented my ascertaining whether any differ- 

 ences would appear in the later development. 



An attempt was made to remove some of the chromosomes 

 during the first cleavage, but the spindle was so much more viscid 

 than the surrounding yolk that no part of it could be sucked out 

 without removing all of it. In some sections the spindle was 

 shown pulled to the surface of the egg but not very much 

 distorted. 



Eggs from which chromosomes were removed were mixed with 

 sperm of a species of Synapta, but did not show signs of devel- 

 opment save for the separation of the " fertilization membrane " 

 from the egg. 



In the experiments on the Asterias egg the following precau- 

 tions were used : The starfish were washed in a strong stream of 



