706 MR FRANK J. COLE 



slightly separated for a short distance at and in front of their origin, but for the 

 greater part of their course they are closely opposed at the mid-ventral line, so that in 

 some specimens the division is not obvious. 



As the two heads approach the ventral margin of the mouth they become 

 more concentrated, and the lateral head assumes a more ventral position, so that just 

 behind the mouth the muscles of both sides form four small compact bundles, consisting 

 of the four distinct heads, two on each side of the mid-ventral line. As the fibres 

 turn abruptly round the anterior margin of the internal bar of the anterior segment of 

 basal plate internal to the tendon of the copulo-glossus superficialis {i.e. in the relaxed 

 condition), the four heads pass simultaneously into the single median tendon, which is 

 narrowest at this point. The anterior margin of the basal plate is distinctly pulley- 

 shaped — due to the external bars with their pads of soft pseudo-cartilage (cp. Part I., PL II. 

 fig. 10), and this confines the tendon to the median portion of the anterior edge of the 

 basal plate. In one specimen the two median heads fused at about the middle of 

 their course, and were finally joined just behind the formation of the tendon by the 

 two lateral heads, the whole mass presenting a bilobed anterior extremity where it 

 passed into the tendon. How much is seen of the tendon ventrally depends, of course, 

 on the position of the dental apparatus. 



According to P. Furbringer, the two heads of each side first fuse up and then pass 

 into a tendon, and the two tendons thus formed unite to form the median tendon. In 

 one series of sections the median head of each side first of all splits into two, the 

 two median halves first fusing up, and the resulting median mass then fusing with the 

 lateral lobes. In this way three muscle masses are seen in transverse section — a large 

 median one, which equals both the median heads, with the smaller lateral head on each 

 side. Subsequently all three fused up, and the single mass so formed finally split into 

 two at its anterior extremity, as mentioned in another case above. The conditions are 

 doubtless subject to much variation. 



The tendon of the muscle first appears on the lateral surface of the lateral heads, 

 and then spreads inwards over the dorsal surface only of the muscle, to fuse in the 

 middle line, and thus form the median tendon, as seen in dissections. This, after the 

 bend, now passes straight backwards towards the dental apparatus, becoming rapidly 

 wider as it proceeds, and is inserted into practically the entire anterior border of the 

 anterior arch of the dental plate (cp. Part I., fig. 7, c. g.jp.). As the tendon approaches 

 the dental plate its histology changes, until it resembles a weak form of soft pseudo- 

 cartilage. In fact, the sections irresistibly suggest the view that the anterior arch of 

 the dental plate is merely a chondrification of the tendon of this muscle (cp. 

 Schafper (16). 



P. Furbringer states, in opposition to the statements of J. Muller, that the tendon 

 of this muscle does not terminate at the anterior margin of the anterior arch, but that 

 it is continued over this on to the posterior arch, and over this again to fuse with the 

 tendon of the retractor muscle of the dental apparatus (longitudinalis linguae). 



