392 
E. EAY LANKESTER. 
penetrate into the neural canal. They appear to be segmentally 
arranged in pairs at regular intervals, as described by Rolph, 
Langerhans, and Schneider ; and for the present their morpho- 
logical and physiological significance is altogether unknown. 
The Neuraxial Canal. — The central canal of the myelon 
of Amphioxus must necessarily be cited in an enumeration 
of the spaces within the body of that animal. Expanding 
to the form of an oval cavity in the anterior region of the 
myelon, which may justly be called the brain, the canal is 
extremely small and narrow throughout the rest of the cord. 
It does not become the seat of any distorting action in pre- 
served specimens, and therefore no more need be said of it here. 
It is worthy of remark that a perineural lymph-space, 1 which 
in some Vertebrates is largely developed between the myelon 
and the neural skeletal sheath or spinal canal, seems to have 
no existence in Amphioxus. The connective-tissue tube or 
canal which forms the skeletal protection of the myelon in 
this animal seems to adhere closely to the nervous tissue, and 
it is rare to find, even under the influence of the most violent 
action affecting other parts of its structure, a separation of the 
skeletal sheath and the contained nervous tissue. In rare cases I 
have observed such a dislocation, as also a case in which the 
true notochordal tissue was also displaced or shrunk from its 
investing connective-tissue sheath (in fig. 1, PI. XXXVI A). 
The Intra- skeletal Lymph-spaces of the Myotomes and 
Myoccelomic Pouches of the Head. — Professor Hatscliek, in 
the ‘ Anatom. Anzeiger,’ August 15th, 1888, has published an 
extremely valuable though brief account of his observations on 
the development of the myotomes and skeletal tissue of Am- 
phioxus. Two of Professor Hatschek’s figures are reproduced 
in PI. XXXVI A, figs. 6 and 7. The division of the primary 
segmental coelomic pouches each into a dorsal portion (proto- 
vertebra or Urwirbel) enclosing the “ myocoel,” and a 
ventral portion (lateral plate or Seitenplatte) enclosing the 
“ splanchnocoel,” is described. 
1 In front of the termination of the nerve-cord there is a small space within 
the neural sheath filled with coagulable liquid (PI. XXXVI A, fig. 3 b). 
