DEVELOPMENT OF THE EMBRYO. 23 



myself of the normal activity of the later stages, I 

 have even fished in the sea at twelve o'clock at night, 

 at which time the earlier segmentation stages were to 

 be found. 



To follow the closing of the gastrula-mouth in fully 

 normal stages, it is a good thing again to fish in the 

 sea on the next morning after the spawning. It is 

 then in the early hours of the morning that embryos 

 are to be found with a wide-open gastrula-mouth, 

 somewhat younger than in Fig. 26. In the case of all 



y o o 



these embryos fished on the morning of the first clay, 

 there is a certain and complete development to be 

 observed, with the exception of those which have per- 

 haps been injured by the net. 



In this way I easily obtained a large quantity of 

 embryos of entirely normal development, and these 

 too underwent in my glasses a further development 

 which was quite normal. This I learnt by a com- 

 parison with the further stages fished at Pantano. 

 From the gastrula stage on the eggs are far less sus- 

 ceptible to outside influences than immediately after 

 their liberation, and during the segmentation. 



With this material I was able again to pursue the 

 fu.rth.3r development in stages following each other in 



