No. I.] DESMOGNATHUS FUSCA. 255 



Metencephal. — From this segment are given off the ninth, 

 tenth, and eleventh cranial nerves. It tapers gradually into 

 the myel. The cavity expands in the region of the cerebellum 

 and these lateral wings may possibly be analogous to the lateral 

 recesses or parepicoeles of higher forms. In its caudal direc- 

 tion the cavity becomes quite narrow and high, but slopes quite 

 abruptly to form the myelocoele. The metaplexus, the roof of 

 the metacoele, is quite compact and quadrangular in outline. 

 It seems to shut off all connection between the cavity and the 

 outside, and I was not able to find any trace of a metapore or 

 foramen of Magendie as has been described by Mrs. Gage in 

 this region of the Dieniyctyliis. 



Myel. — The myel is a subcylindrical cord presenting very 

 slight enlargements in the cervical and sacral regions. At the 

 foramen magmitn there is quite a marked constriction. There 

 is scarcely an indication of a dorsal furrow, while that of the 

 ventral side is very noticeable and contains quite a good-sized 

 blood-vessel. There is also a dorsal vessel — the spinal vein, 

 but much smaller in size. The membranes have about the 

 same relation as with the brain. There is a greater separation 

 of the dura and pia, and the arachnoid is therefore more fully 

 developed. In the larva the spinal canal is not as nearly filled 

 up by the cord as in the adult and the meningeal relations can 

 be studied to much greater advantage. 



The spinal ganglia are very large, their dorso-ventral diameter 

 being much greater than the lateral. They are situated outside 

 of the spinal canal in the intervertebral foramina. They are 

 enveloped in dura and lie close up against the muscle segments. 

 The majority ot the cells composing these ganglia are large and 

 suggest an analogy to the " periganglionic glands" found in 

 the frog, although no milky fluid nor any evidence of calcareous 

 matter has been found. The ganglia are attached chiefly to 

 the dorsal roots but embrace the distal portion of the ventral 

 roots as well. In the frog the periganglionic glands have been 

 found on the ganglia of all spinal nerves as well as the Gas- 

 serian ganglion of the trigeminus nerve. 



The existence of a ligamentwn dentatiim homologous to that 

 found in higher forms and as described by Biirckhardt for 



