ON THE LAMINAR TISSUE OF AMPHIOXUS, 
423 
1. The dermis. 2. The subdermic layer. 3. The sub- 
cutaneous aponeurosis. 
1. T/ie dermis^ is formed, as in fishes and Amphibia, of a 
thin layer which appears in section to be homogeneous, and 
'\Vhich "in Amphioxus presents upon its external surface a 
double rectangular striation, wfith the crosses corresponding 
to the nerve terminations which Langerhans^ has so well 
figured. 
2. Subdermic layer . — The subdermic layer^ is charac- 
terised in Amphioxus by the presence of a large amount of 
structureless substance. This latter is as usual absolutely 
hyaline, and keeps this character even after the action of 
osmic acid in saturated solution.^ It is traversed by fibres 
having the character of laminar fibres, stretching from the 
deep face of the dermis to the subcutaneous (cf. fig. 3a). 
These fibres are absolutely devoid of any nucleus and of any 
division into cells, a fact not without interest as bearing 
upon the much debated history of the genesis of the laminar 
fibres. We have pointed out in the following terms^ the ex- 
istence of similar fibres in the lophioderm of larval Axolotls 
measuring 60 to 80 mm. in length : In sections cut la 
planchette,^ after treatment with osmic acid, the amorphous 
matter is seen to be traversed by vessels and nerves, and to 
enclose some fibro-plastic cells with regular spaces between 
them, invisible ; but extremely fine laminar fibres are also 
seen. These run from the skin of one side to that of the 
other, in the same manner as the strings in an instrument 
in a very beautiful manner, all parallel to one another. These 
fibres seem, therefore, to have no relation to the fibro-plastic 
cells.” 
It was always difficult in Axolotl to pronounce an opinion 
on the independence of the fibres and cells on account of the 
presence of the latter. Whilst in Amphioxus there are no 
fibro-plastic cells furnished with any prolongations from 
which laminar fibres might be derived. These are also 
larger than in Axolotl, and are more deeply stained by car- 
mine. No migratory corpuscles are found in the hyaline 
structureless portion of the subdermic tissue of Amphioxus. 
3. Subcutaneous aponeurosis . — This membrane appears in 
^ “ Cutis Oder Lederhaut,” Stieda. 
- Loc. cit., fig. 13. 
3 “ Das Unterhautgewebe ” of Stieda. 
^ For the action of this reagent see Pouchct, “De I’emploi dcs solutions 
concentrees d’acide osmique,” ‘ Journal dc I’Anat.,’ Sept.-Oct., 187C. 
^ G. Pouchet et Tourneux, ‘ Precis d’histologic huinainc ct d’histo- 
genie,’ 1878, p. 102. 
