59 



T.ovement begins it rese'-bles an unsegr.entod egg vory nuoh, 

 except that instead of being snherical it is nov/ oval. 

 In si.";e it is about the sa~e as the unsegr.ented egg, if 

 anything rather sr.aller. The decrease in size "ust be ac- 

 counted for by the fact that scrr^e of the yelk has been di- 

 gested; and the larva evidently has - ot yet acouired any 

 means of receiving food .fro::i the external world. 



The larva rer.ains i- this oval conditio:- for soine 

 hours, after v;hich it elongates to form a tyoical "lanula. 

 I'/hen the embryo is twenty-four hours old it lengthens out and 

 becomes more slender and assumes a general aDpearance as shovm 

 in Figure 23, As it becomes older it grows still longer, 

 figure 24 shows a larva of thirty hours. It has now the 

 power of c^ntra-tion; and is sensitive to stiuli. When 

 the cilia a.e first developed and for some time during the 

 oval condition of the larva it swims near the botto- of 

 the aquarium. But as it grows longer and elongates it rises 

 in the water and s'.vi:,s at or near the surface. The length 



