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were not known long ago, than that there should be any particular 
difficulty about them. 
Given the presence of ganglionic elements in the myotomes, one 
would naturally enquire what function they fulfilled, and how they 
got there. A motor function might almost be assumed from the 
' position; but when the point may be solved by diligent observation, 
any assumption is out of place. 
The motor function is rendered certain by the following circum- 
stance. In later stages, i. e. in embryos of 40—45 mm. in length 
these ganglion cells lie embedded in a mass of muscle substance. 
Actual instances of this will shortly be described, and evidence adduced 
for the motorial nature of all the transient nerve fibrils to the myotomes. 
How came the ganglion cells into the latter? In dealing with 
the subject matter of this paper I have kept as free as possible from 
bias, and have held myself prepared for any eventuality. All stages 
of the wandering of macro-ganglion cells to the myotome were to be 
found; but it was not so easy to meet with cases in which the 
ganglion cell could be seen forcing its way into this structure. This 
can indeed be proved to take place in many instances; but, looking 
carefully over the sections of younger embryos, other factors were 
noticeable. - The phenomenon of fig. 5 was remarked in several speci- 
mens of 22 mm. and upwards; and therefore further light on the 
matter was to be expected from the examination of slightly younger 
embryos. 
In one of 20—21 mm. in length the appearances depicted 
in fig. 6 were detected. This, again, is not an isolated case. When 
Fig. 6. Transverse section of a 
R. batis of 21 mm. 
it first met my eye, it reminded me in a striking manner of what 
I had found to be the mode of origin of the egg-cells in Myzostoma’). 
1) These results have not yet been published. 
