TERMINATION OF MOTOR NERVES IN VERTEBRATA. 225 



have hitherto been regarded as unstriated, of Helix pomatia and 

 of Bowerbankia. According to him, a fine nerve fibril enters 

 the large muscular fibre cells of the muscular apparatus of the 

 foot of Helix pomatia near their centre, divides immediately in 

 their interior into two branches, which extend to the two 

 pointed ends of the muscular fibre in the form of two elon- 

 gated, and towards their extremities spirally twisted, threads. 

 In the centre, and just subjacent to the point of division, an 

 ellipsoidal accumulation of finely granular substance exists. 

 In Bowerbankia, whose muscles Trinchese likewise describes as 

 smooth bands, only a low conical process of the somewhat 

 broader nerve fibre is present, in which cone, and at its base 

 where it touches the muscle, is the granular material with a 

 spherical nucleus and nucleoli. 



The question now arises, what is the essential nature of the 

 termination of the motor nerve ? The author cannot doubt 

 that this is at present most imperfectly known in the Arthro- 

 poda. Kouget, indeed, states that he succeeded in perceiving 

 a prolongation of the axis cylinder in the nerve eminence in 

 the form of a system of branched fibres ; and we must probably 

 admit that this system does exist : but the further statement 

 of Rouget, who attributes nervous properties to this part alone, 

 as was generally previously admitted in Germany, and that this 

 ramified system of fibres lies beneath the nucleated substratum, 

 appears to the author to be very much in need of confirmation. 

 Engelmann, who also examined the muscles of the Arthro- 

 poda, depicted a transparent homogeneous and quite vesicular 

 mass at the apex of his nerve eminence, which appears to be 

 the analogue of the terminal nerve plate found in Reptiles and 

 Mammals, and, like these, to be bounded throughout the greater 

 part of the surface turned towards the contractile substance by 

 a granulated substratum. If this supposition be established 

 namely, that in the Arthropoda also a non-granular plate, or 

 even a structure similar to the intra-muscular axis-cylinder 

 system of the Amphibia is present, covering the granular 

 nucleated substratum, to which Rouget's statements appear to 

 point we should have obtained the much-desired uniformity 

 of structure; and there would then be one mode of nerve 

 termination, in which the nerve ends with a motor plate in a 



