ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 611 
the time that the cellular structure of tissues was first studied. It is 
true that more recent researches have enlarged our knowledge of proto- 
plasmic continuity, but it is still a phenomenon far from being of such 
universal application as to constrain us to abandon that very useful 
morphological concept, a cell. The study of cells has indeed in recent 
years been carried on by many authors with a minuteness which a 
short time ago was undreamt of. Nothing can be more clear than the 
fact that, in Nereis or in Unio, there result from the division of the ovum 
separate protoplasmic corpuscles, as distinct from one another as one 
room in a house is distinct from another. To each blastomere, it may 
be said in figurative language, is given material which it must place, 
not anywhere, but at one particular part of the edifice. The results of 
E. B. Wilson and others are such that it is no exaggeration to say 
that they effectually dispose of the idea that a syncytial theory of animal 
organisation is of general application ; nay, more, they show that in not a 
few instances cells possess a morphological and physiological significance 
greater than was at one time supposed. Mr. Bourne thinks that the 
evidence is overwhelming that there are numerous cases in which there 
is not “ a primitive continuity which has never been broken.” Mor- 
phologists would appear to be amply justified in refusing to recognise 
Mr. Sedgwick’s views as to the syncytial nature of animals, and there is 
no justification for the strong language which he uses towards them on 
account of their refusal. As to the fact that any reputable zoologist 
has stated that an organism is composed of independent and isolated 
units there appears to be no good evidence. Prof. Haeckel has been 
claimed as the author of the doctrine that an animal is a cell-republic, 
but, as a matter of fact, Haeckel stated this of a plant as opposed to 
the animal, while the researches of Mr. Walter Gardiner have shown 
that the statement is not true of plants. Mr. Sedgwick’s critic is quite 
certain that the picture which he drew of the teaching given to every 
student of biology is a travesty of the truth. Zoologists and botanists 
alike have long been possessed of the truth that there is no fundamental, 
but only a formal distinction between unicellular and multicellular 
organisms. At the same time it is to be admitted that the cell theory 
has been very differently treated by various authors. After pointing 
out the now recognised importance of a nucleus to a cell, Mr. Bourne 
deals in a critical manner with various forms of which it is difficult to 
say whether or not they should be called single cells. In the cases 
where several nuclei are present in one mass of protoplasm it has been 
urged that the test of unicellularity is not the number of the nuclei, 
but the fact that the protoplasm is continuous. The definitions of some 
authors would bind us, but biologists do not want to be bound ; and if 
we are to be free, we must, Mr. Bourne thinks, take refuge in some such 
lax but comprehensive statement as that of Yon Sachs, namely, that 
cell-formation is a phenomenon very general in organic life. Even if 
we must regard it as only of secondary significance, it is a characteristic 
expression of the formative forces which reside in organic substance. 
The truth appears to be that the attempt to frame short concise defini- 
tions, applicable without exception to whole classes of phenomena, leads 
to trouble. There is no place in biology for definitions as exact and 
universal as those of geometry. To attempt to form definitions, to 
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