144. GILBERT 0. BOURNE. 
effectually disposes of the idea that a syncytial theory of 
animal organisation is of general application. 
It does more than this, it shows that there are not a few 
instances in which cells possess a morphological and physiolo- 
gical significance greater than was at one time supposed. 
There are numerous other cases in which, at an early stage 
of development, cells wander far from the position in which 
they originated, and become placed so far from the parent 
cells from which they sprung, that any idea of protoplasmic 
continuity is impossible. As examples I may mention: the 
outer layer cells of Cornacuspongiz and Silicispongiz, which, as 
Maas has shown, go through remarkable migrations ; the me- 
soblast of Callianira bialata, Beroe and Cydippe, as de- 
scribed by Metschnikoff, whose statements are confirmed by 
observations made (but unfortunately not published) by Mr. 
Riches on Hormiphora plumosa; the lower endoderm 
cells of Discocclis, Eurylepta, and Leptoplana, as described 
by Lang, Hallez, and Selenka. 
In short, the evidence is overwhelming, and it must be 
taken to be very clearly established that there are numerous 
cases in which there is not “a primitive continuity which has 
never been broken.” 
It is apparent, then, that morphologists have been 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. 
It is, on the other hand, quite possible that the frequency of 
the occurrence of protoplasmic continuity between developing 
tissue-cells may have been overlooked or ignored by a few 
authors, and that those who have done so have been led into 
the error of attributing too great and too fundamental im- 
portance to the cell as an independent vital unit (Lebenseinheit). 
But, in point of fact, I am unable to find, in the writings of 
any reputable biologist, any statement to the effect that an 
organism is composed of independent and isolated units. One 
may, it is true, find passages here and there which, when 
