ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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may be described as cellular is not a theory at all. It is a statement 
of fact, and no more a theory than is the assertion that sunlight is 
composed of all the colours of the spectrum. The theory comes in when 
we try to account for the cellular constitution of organisms, and it is 
this theoretical part of the “ cell-theory,” and the point of view it makes 
many of us assume, that he condemns. Mr. Sedgwick is not at issue 
with the word cell, for structures most conveniently called cells 
undoubtedly exist, and he fully agrees that the phenomenon called 
cell-formation is very general in organic life ; but at the same time he 
bolds with Sachs and many others that it is not of primary significance. 
The author’s work on Peripatus first led him to doubt the validity of 
the current view of the origin of the Metazoan body. In the first place, 
he found that in some forms there is no complete division of the ovum, 
und on examining the facts he discovered that such forms were more 
numerous than had been supposed. It therefore appeared that, in some 
Metazoa, the ovum divided into completely separate cells, while in 
others it did not so divide. The question then arose, which of these 
methods is primitive. The answer naturally was, the complete division, 
because this fitted in with our ideas as to the supposed evolution of the 
Metazoa from a colonial Protozoan ; but on reflection this difficulty arose : 
the individuals of colonial Protozoa are in protoplasmic connection, 
while the cells of the completely segmented ova are separate. In an 
important particular, therefore, the parallel between the ontogeny and 
the phylogeny breaks down. It was possible, therefore, to entertain the 
view that the differentiation of the Metazoa had been effected in a con- 
tinuous multinucleated plasmatic mass, and that the cellular structure 
had arisen by the special arrangement of the nuclei. Since his researches 
on Peripatus, Mr. Sedgwick has paid attention to Vertebrates, and has 
found that a number of embryonic processes have beeh wrongly described. 
He thought he could trace the errors to the dominating influence of the 
cell-theory in its modern form. A theory which led to obvious errors 
must surely be wrong, and Mr. Sedgwick consequently denounced it ; 
but this denunciation in no way implied a failure to recognise the so-called 
cellular structure of organisms, or their origin from the one-celled ovum. 
Ou the contrary, what he was led to, was a reconsideration of the 
question, what is the meaning of the predominance of the structure 
called cellular? In answer to Mr. Bourne’s criticism, that he cannot 
ascertain from Mr. Sedgwick’s article the latter’s views on the cell- 
theory, it is asked why he should expect or wish to discover them. 
Mr. Sedgwick’s remarks were simply directed to show the shortcomings 
of the theory with regard to certain anatomical facts. He thinks that 
Mr. Bourne has been unfortunate in selecting Prof. Haeckel as an ally, 
in consequence of his having completely failed to grasp the German 
naturalist’s meaning. He points out that much of Mr. Bourne’s essay 
is taken up with discussing the meaning of the word cell, and he asks 
if it is likely that, when so much discussion is required to arrive at the 
meaning of the word cell, there will be simple agreement as to the theory 
which is supposed to explain and account for the so-called cellular 
constitution of organisms. In fact, he thinks that Mr. Bourne is in 
substantial agreement with him in his condemnation of the theoretical 
part of the cell-theory. 
