THE DEVELOPMENT OF LEPIDOSIREN PARADOXA. 451 



nerves have considerable bearing upon some not unimportant 

 questions of general morphology. 



1. I have shown that those muscle-cells of the myotome 

 whose investigation is easy are already in organic connection 

 with the nervous system while they lie in close apposition to 

 it. As these muscle-cells are carried further and further away 

 from the nerve-centre by the interposition of mesenchyme, 

 and by the action of differential growth, they trail behind 

 them the ever-lengthening nervous strand/ and there is 

 therefore no question about calling in — so far as regards 

 these particular muscle-cells — either a growth outwards 

 towards them of freely ending nerve-trunks or their pro- 

 vision with nerves through the conversion into nerve of 

 other tissue. They are connected while still close to the 

 nerve-centre with a potentially nervous bridge, and as 

 development goes on this merely increases in length and 

 thickness. 



That this holds I have been able to definitely establish 

 only in the case of certain muscle-cells in the region of the 

 myotome nearest the nerve-root, but it is extremely unlikely 

 that motor nerves do not develop all according to the same 

 general plan. They probably all develop just as do those 

 which I have described. 



2. I have shown that in the young Lepidosiren there 

 exists in the myotome a neuro-muscular apparatus of an 

 extraordinarily primitive character — a simple though enlarged 

 epithelial cell with contractile fibres developed in the peri- 

 pheral regions of its protojDlasm, and with its cell substance 

 passing out at its inner end into a kind of tail which is 

 continued along the nerve rudiment, doubtless to pass — 

 though this would be very difficult to demonstrate — at its 

 central end into a nerve-cell in the neural tube. 



The full consideration of muscle development will come 

 in a later part of my work, but even in passing I think we 



' Tliis of course explains quite clearly the meaning of the rectilinear course 

 of youns; nerves, upon which His and others lay stress. Cf. 'Arch. Anat. 

 Phys.,' 1887, S. 375. 



