172 



F. H. EDGEWORTH. 



myotome. Both these Anlagen are anterior projections from 

 the upper ends of their respectiv^e myotomes, to add to the 

 musculature of the eye, which is primarily formed from the 

 pre-7iiaudibular segment. 



As above stated, the lateral plate of the mandibular 

 segment, which is serially homologous with that in the hyoid 

 segment, may be regarded as the myotome of that segment. 



In the case of the five branchial segments, the epithelium- 

 lined cavities — the lateral plates of van Wijlie — are con- 

 tinuous below with the cephalic coelom. Above, tliey are 



Text-pig. 4. 



-W^^ok^>>^>^- 



Oiipk .<jxl 



Scyllium, embryo 14 mm., transverse section. 



stated by van Wijhe to be continuous with myotomes — his 

 sixth, seventh, eighth, and ninth. These myotomes were 

 stated to separate from the lateral plates, and to undergo 

 various chaTiges, the fifth atrophying, the sixth becoming 

 very rudimentaiy, and the seventh, eighth, and ninth forming 

 " Vom Schiidel zum Schultergiirtel ziehende Muskeln nebst 

 dem vordersten Theile des sterno-hyoideus." In regard to 

 this asserted continuity between the myotomes and lateral 

 plates, it is noteworthy that Ziegler says it is " schwierig den 

 unten Ursprung des Ursegments mit dem oben sichbaren 

 Myotoni in A^erbindung zu bringen, und dies ist bis jezt 

 keinem einzigen Forscher in dfr richtigen Weise gelungen." 



