158 ' DR. F. E. BEDDARD ON 



divided off the cortical from the medullary parenchyma and lay 

 therefore at a distance from the outside of the body of about 

 one-third of the entire vertical diameter on each side ; that is to 

 say, the medullary parenchyma in this species is of about the 

 same diameter as the cortical layer. The fibres are strong and 

 are disposed in a layer which varies from one to three fibres 

 thick. They stand out so conspicuously from the general paren- 

 chyma of the body that it would be impossible to miss them. In 

 Ophidotcenia this layer, although in reality plain enough, does not 

 strike the eye so forcibly. I am indeed reminded by their appear- 

 ance of the figure of the same muscles in Palciia varani given in 

 his account of that species by Dr. Shipley * ; and it will be 

 remembered that I have myself ventured to consider that 

 Palaia may be really identical with Ichthyotcenia, or at least 

 near to it t- 



This layer of longitudinal muscles does not form a complete 

 layer surrounding the medullary parenchyma. It is interrupted 

 at its two ends by the nerve-cord which is partly within and 

 partly without the medullaiy region. Dr. Schwarz has laid some 

 stress upon the fact that the transverse layer of mviscular fibres 

 in the genus Ichthyotcenia at least occasionally runs within the 

 medullary parenchyma, occupying the greater part of that region, 

 and the figure already quoted from Dr. Shipley's memoir shows 

 something of the same kind in Pcdaia varani. There is no doubt 

 that in Ichthyotcenia gabonica the medullary parenchyma is per- 

 vaded by slender muscvdar fibres running transversely and 

 scattered through it fairly uniformly, but not anywhere very 

 close together. I imagine that this is the same appearance that 

 has been seen and described by the two authors quoted. These 

 fibres are definitely muscular fibres, and not the usual paren- 

 chymal meshwork arranged in a more markedly transverse 

 fashion. The last point in the general structure of the body to 

 which I shall refer is the subcuticular layer. This layer is 

 several cells thick ; but it is by no means so conspicuous as in 

 Acanthotcenia and Ophidotcenia and apparently in some other 

 species of Ichthyotcenia, since in these three genera the indi- 

 vidual cells are much larger than in Ichthyotcenia gabonica. 



In more mature segments (see text-fig. 34) the layer of 

 muscular fibres lying between the cortical and medullary 

 regions is not at all defined in transverse section. Instead of 

 a clear cut row of fibres, a denser layer of parenchyma seems 

 alone to divide the cortical and medullary regions. In longi- 

 tudinal sections, however, this dense layer is seen to be traversed 

 by delicate longitudinal fibres one or two deep ; these are not 

 apparent at all in transverse sections unless the latter happen to 

 be cut rather obliquely, in which case the fibres become visible. 

 This difference between the longitudinal muscular layer in 



* " Zoological Results . . . from New Britain, New Guinea, etc.," by Arthur Willey, 

 Cambridge, pt. v. 1900, pi. Iv. tig. 18. 

 f P. Z. S. ?oe. cit. 



