I06 MARINE BIOLOGICAL LABORATORY. 



modify it in its essential points in the least. They are 

 merely suggestions which have developed during the 

 consideration of the application of the theory, and must 

 be regarded simply in that light. For a complete exposi- 

 tion of them much more detailed description, unsuitable 

 for an occasion of this kind, would be necessary, and I 

 present them here merely in the hope that they may 

 incite to more thorough and perfect acquaintance with 

 the problems connected with the early development of 

 invertebrated animals, and the bearings of the onto- 

 genetic phenomena on the question of the origin of the 

 Metazoa and of their organs. I cannot do better than 

 quote in conclusion from Metschnikoff, '' Es vmsste 

 gerade im Bereiche der niederen Metazoen eiii fester 

 Bo den fiir das Verstdndnis der primitiven Organe gewon- 

 neii werden!' 



