36 BASIC METHODS FOR EXPERIMENTS 



ment as soon as they are laid. The egg of Aplysia is very 

 hardy and stands up well ujider laboratory conditions. I have 

 kept eggs developing perfectly for two weeks after they had left 

 the jelly strings (at Roscoff). 



Loligo 



The squid, Loligo pealii, commonly found on the Atlantic 

 coast of America, will breed in laboratory tanks provided they 

 are not overcrowded and the sea-water does not flow too force- 

 fully. By keeping the animals under observation, one can follow 

 copulation and egg-laying as described by Gllman A. Drew 

 (191 1). In this fashion one can obtain eggs In various stages of 

 development. Since the females tend to deposit the egg-strings 

 in the same place, it Is best to keep the animals in separate pairs. 



Eggs removed from the female can be readily fertilized; 

 development in this "case is normal. The mechanism of the 

 discharge of the spermatozoa, as worked out by Drew, is an 

 interesting phenomenon worthy of observation. 



Cynthia, Molgula, Ciona 



According to Conklln (1905), "the eggs of Ciona and of 

 Molgula are laid in the early morning, a little before daybreak, 

 while those of Cynthia are laid In the late afternoon, a little 

 before sunset." He also states that a large proportion of the 

 eggs of Cynthia never develops if fertilized although eggs seem 

 ripe and the spermatozoa active. He found It best, therefore, 

 to use normally laid and fertilized eggs. It is my experience 

 that, although It Is best to use normally shed eggs and sperma- 

 tozoa, ascidlan eggs removed from the animals fertilize In high 

 numbers if they be thoroughly washed free of body fluid. 



Eggs of Ciona taken from the animals fertilize readily. At 

 Naples, at least, eggs and spermatozoa taken from the same 

 individual and mixed give as good development both as to per 

 cent, and as to quality as those obtained by mixing eggs and 

 spermatozoa from different individuals. (Fuchs, 1914; Just, 

 1934.) Thus my experience with respect to self-fertilization in 

 Ciona Is similar to Fuchs'. Perhaps the failure of Alorgan and 

 of others to obtain self-fertilization in this animal at Woods Hole 

 was due either to the poor condition of the animals which they 

 used or to insufficient numbers of them. I suspect in Morgan's 



