382 ON THE ANATOMY OF AMPHIOXUS LANCEOLATUS. 



— au external, apparently longitudinal ; an internal, trans- 

 verse. 



The only muscle in the Lancelet for performing a special 

 function is a flat bundle, connecting and bringing together the 

 two halves of the hyoid apparatus, for the purpose of closing 

 the mouth. 



Under the microscope the primitive fibres of the lateral 

 muscles exhibit the usual transverse strise, but are not collected 

 into fasciculi, constituting immediately the mass of the tissue. 

 Transverse strise are not observable in the fibres of the 

 abdominal muscle. 



In festival System. 



This system appears as a tube passing nearly in a straight 

 line from mouth to anus. It consists of two portions — an 

 anterior, large and dilated, and appropriated to the respiratory 

 function ; and a posterior, small, of pretty uniform calibre, 

 and constituting the proper digestive apparatus. The res- 

 piratory portion of the canal will be described afterwards in 

 connection with the vascular system. The mode in which 

 the digestive communicates with the branchial department 

 of the tube could not be satisfactorily made out. It 

 appealed, however, that the branchial cavity, becoming- 

 smaller, curved slightly of itself towards the left side, 

 and then proceeded directly, and without any change in its 

 calibre, to the anus. The anus is in the form of a longitudinal 

 slit. 



There is not the slightest trace of a liver, or of any other 

 assistant chylopoietic viscus. The gut was full of a brown 

 granular matter, tinged, probably, by a bilious secretion from 

 the walls of the bowel. 



Respiratory System. 

 Tin's system is constituted by the anterior compartment of 



