216 ADAM SEDGWICK. 



they were really connected by protoplasmic strands which had 

 escaped observation. But, on the other hand, there was the 

 possibility that the completely segmenting ova were secondary 

 acquisitions of ontogeny, and that the development in such 

 forms as Peripatus, Alcyonaria, &c., was more primitive, and 

 that the passage from a Protozoon to a Metazoon had taken 

 place by way of a form more resembling a multinucleated 

 cilated Infusorian than Volvox. In other words, that the 

 differentiation of the Metazoa had been effected in a continuous 

 multinucleated plasmatic mass, and that the cellular structure 

 had arisen by the special arrangement of the nuclei in reference 

 to the structural changes. This was the stage to which ray 

 researches on Peripatus led me. Since then I have paid 

 attention to Vertebrata, and I have found that a number of 

 embryonic processes have been wrongly described, amongst 

 them such important matters as the development of nerves 

 and the origin of the mesoderm ; and I thought that I traced the 

 errors referred to to the dominating influence of the cell-theory 

 in its modern form, for the facts seemed so obvious in them- 

 selves that it would have been impossible to make any mistake 

 about them had they been examined without the prejudice 

 imparted by a preconceived theory. A theory which led to such 

 obvious errors must, I thought, be wrong, and I denounced it. 

 But my denunciation in no way implies that I fail to recognise 

 the so-called cellular structure of organisms or their origin 

 from the one-celled ovum. On the contrary, I was led to a re- 

 consideration of the question, what is the meaning of the pre- 

 dominance of the structure called cellular, which is characterised 

 by a definite relation of the nuclei to the functional tissues, 

 and of the fact that the organism so often passes through a 

 unicellular stage. With regard to the former I must say 

 that I have arrived at no conclusions which enable me to 

 formulate to myself any satisfactory hypothesis, and, as 

 I stated at the outset, I do not think it is possible 

 to do this until we acquire some more understanding of 

 the relative function of nuclei and protoplasm. But with 

 regard to the latter there are some facts which might 



