218 - ADAM SEDGWICK. 



•Will find the mesenchyme described or figured as consisting of 

 branched, isolated cells. 



Mr. Bourne then refers to certain remarkable researches 

 which emphasize the distinction and complete isolation of the 

 cells formed in the segmentation of the egg; with what object 

 is not apparent, for he proceeds on the next page to condemn 

 those who hold that the organism is constituted of independent 

 and isolated units. He even maintains that no reputable bio- 

 logist holds such a view. However that may be, I do not 

 think that his quotation from Haeckel in support of his con- 

 tention is a happy one, for it is perfectly clear from the quota- 

 tion that Haeckel, who indeed goes so far as to call the units 

 individuals, holds the view which Mr. Bourne condemns. 



Haeckel even calls them individuals of the first order, and 

 says that in the adults th^y frequently unite to form colonies ; 

 and he particularly implies that the loss of independence 

 caused by their colonial union is secondary. Mr. Bourne 

 has completely failed to grasp Haeckel's meaning, else how can 

 he write as he does on the same page with the quotation from 

 Haeckel — "So that, as a matter of history, while plants used 

 to be considered to be colonies of independent life units-, 

 animals were not." 



The most remarkable part of Mr. Bourne's criticism 

 is that in which, after strongly animadverting on my 

 statement that it is difficult if not impossible to enunciate 

 the cell-theory in a manner satisfactory to every one, — indeed 

 he quotes from Schwann and Hertwig to show how precisely 

 it can be stated, — he proceeds to devote a dozen or more 

 pages of his paper to a consideration of the various views 

 which are held and which may be held as to what a cell 

 really is ! If this amount of discussion is required to arrive 

 at the meaning of the word cell, is it likely that there will 

 be simple agreement as to the theory which is supposed to 

 explain and account for the so-called cellular constitution of 

 organisms ? 



Again he says, referring to my description of the embryonic 

 mesoderm as a protoplasmic reticulum with nuclei at their 



