— 164 — 
Fig. 99 represents a cell with a such structure. The light circular 
area x is very distinctly defined. There is a very long nucieus (jY), 
with some protuberances, situated in one side of this area, in the 
centre there is another somewhat lighter corpuscle (iV') which is perhaps 
also a nucieus. I could, however, see no cells in this area, and 
whether it is one cell or contains several cells or what it is, I can 
not decide. 
The nuclei of the spinal nerve-cells are large and exhibit gener- 
ally a distinct chromatin reticulation. 
On comparing the main characters in the structure of the 
nervous elements of these two vertebrates {Amphioxus and Myxine) 
with what is previously described in this paper, we will see that there is 
the most perfect correspondence in this respect between the inverte- 
brated bilaterates and these inferior vertebrates. But as we can 
not easily suppose that their is any principal difference between 
them and higher vertebrata in these respects, we may thus assume 
that the principal results arrived at in this paper are applicable to 
all bilaterates. In a future paper I hope to be able to pay a more 
special attention to the nervous elements of the vertebrata. 
60 The combination of the nerve-tubes with each other. 
A question of much interest arises, viz. how is the combination, 
between the nerve-tubes produced, or rather how is the impression 
received by a sensitive nerve-tube conveyed to a motoric one. To 
express it in another way me may say, which elements has an 
irritation of a sensitive nerve-tube to pass, to produce a reflex- 
movement.?^ 
A very common theory is, as is well-known, that an irritation 
of a sensitive nerve-tube passes to a » sensitive « ganglion cell, then, 
from this cell, through a protoplasmic process to a motoric ganglion 
cell, and from that cell it passes into a motoric nerve-tube to 
produce a reflex-movement. In a previous chapter (ch. 4, p. 148], 
it is, I hope, suficiently proved, that in the invertebrated bilaterates 
there is no direct combination between the ganglion cells through 
the protoplasmic processes, neither is there in Myxine (as we have 
seen in the previous chapter); the above quoted theory of the 
