714 MR FRANK J. COLE 



anterior half of the belly referred to above. The median division between the two 

 muscles is somewhat early lost in the sections, but I have assumed that the partition 

 b will represent the boundary between the two sides. We now find that the hoop 

 extends vertically, and finally fuses at the mid-ventral line to form a complete circle, 

 which encloses all the muscle fibres present ( = the anterior half of the belly) and also 

 the second division of the ligament, b. All the fibres outside the hoop in 1498 (= the 

 posterior half of the belly) have now died away. At the same time the second or 

 internal portion of the ligament loses its ventral fork, and with it all traces of its 

 paired origin (1260). The outer or circular portion of the ligament next becomes 

 smaller and more circular, and the fibres tend to concentrate below, leaving the dorsal 

 half non-tendinous (cp. 720). Further, the internal tendon loses its vertical sheet-like 

 character and becomes spherical (870). In the next stage (720) we find the dorsal 

 half of the outer circle (a') entirely non-tendinous, all the tendon fibres being con- 

 centrated below in a large median ventral tendon (a), the centre of which is invaded 

 by a weak, soft, pseudo-cartilage. The remainder ot the circle (a') is membranous 

 and lodges the nerves at the mid-dorsal line, whilst the internal tendon has now split 

 up again to form the dorsal paired tendon (lb, 26) separated by a median vertical 

 membranous partition (a"), and with their external membranous sheaths connected 

 below with the dorsal non-tendinous portion (a'") of the ventral tendon. Now the 

 dorsal membranous portion of the circle (a'), then the median partition (a"), and 

 finally the dorsal fibrous portion of the ventral tendon (a"'), fuse with the median 

 ventral wall of the gut. Whilst this is happening (625), the dorsal tendons, having 

 diverged, split vertically into two (lb', lb", 2b', 2b"). The inner of these (lb", 2b") 

 are inserted into the ventro-lateral wall of the gut, and not into the dental skeleton. 

 The outer ones (lb', 2b') cross the posterior arch of the dental plate internally, and 

 become continuous with the tissue bridging the large gap between the anterior and 

 posterior arches of the dental plate at the posterior base of the inner row of teeth. 

 In these two ways the tendon of the longitudinalis linguae becomes intimately related 

 to the gut and the dental mucosa, so that its pull will act on these structures as well 

 as on the dental skeleton. 



The median ventral tendon (a) fuses with the median portion of the posterior arch 

 of the dental plate, and is in fact partly morphologically continuous with it, since a 

 large portion of the tendon becomes converted into soft pseudo-cartilage containing 

 nests of soft cartilage, and thus passes without any hard-and-fast break into the soft 

 cartilage of the posterior arch. Many of the fibres, however, do not terminate in this 

 way, but cross on either side of the posterior arch, to pass over into the stout membrane 

 connecting the two arches of the dental plate, and also partly into the tendon of the 

 copulo-glossus profundus, as described under that muscle. According to Schaffer's 

 latest paper, the whole of the above membrane is invaded by soft pseudo-cartilage, but 

 it is only partly so in my preparations. 



The extension of the dental apparatus is effected by two muscles, the superficial 



