702 MR FRANK J. COLE 



(see Part I. pp. 772-3), but which had no direct connection with the present muscle. 

 The strand above is the transverse tendon or "tether" of J. Muller and P. Furbringer 

 and its object seems to be to provide a pathway under the control of the present muscle 

 for the passage of nerves and blood-vessels to and from the " tongue." Such a movable 

 bridge is, of course, necessary, as the position of the " tongue " is not fixed. 



According to P. Furbringer, the larger part of the fibres of the hyo-copulo-glossus 

 pass into a tendon which is inserted into the ventral [?] surface of the internal bar of 

 the anterior segment of the basal plate throughout its entire length, a small slip being 

 also despatched to the base of the fourth tentacular cartilage. This agrees substantially 

 with J. Muller's account of Bdellostoma, and I therefore feel diffident in questioning 

 its accuracy. Nevertheless I am more than doubtful whether what these authors 

 describe as the anterior tendon of this muscle is not too diffuse and extensive to 

 represent a true tendon of a muscle, and I cannot regard it as other than a portion of 

 the general fascia. It is true that a careful examination of the sections reveals its 

 ventral margin fusing with the dorsal border of the guiding rail of the anterior segment 

 of the basal plate, and in front of this with the large pad of soft pseudo-cartilage on the 

 dorsal surface of the anterior extremity of the same, but it is certainly not connected 

 with the fourth tentacle. Its principal relation is undoubtedly to the mucosa of the 

 mouth as above described, whilst in front of the basal plate it loses its identity by fusing 

 first with the external fascia of the copulo-palatinus and then with the ventro-external 

 fascia of the first or principal head of the copulo-tentaculo-coronarius — thus indicating 

 again that it is only a portion of the general fascia. Furbringer indeed seems to have 

 been here influenced by Muller's description of the muscle. 



An important function of the hyo-copulo-glossus is stated by Furbringer to be that 

 it acts as a tether to the dental apparatus, i.e. prevents by its transverse " tendon " the 

 " tongue " from travelling too far in either direction. Here, again, Furbringer has 

 overlooked the fact that as the play of the latter is necessarily limited by the looseness 

 of the mucosa of the floor of the mouth, such a function is surely superfluous. A much 

 more reasonable explanation of the "tether" is the one I have given above. Furrringer 

 also states that the attachment of the "tether" ventrally at a position intermediate 

 between the anterior and posterior borders of the dental apparatus would assist the pull 

 of the protractors in toppling the latter out of the mouth by acting as a fulcrum. 

 Further, when the "tether" is fully extended forwards, the pull of the hyo-copulo- 

 glossus is said to reinforce the backward drag of the longitudinalis linguae until the 

 " tether " has swung backwards behind the anterior extremity of the belly of the former 

 muscle, when it is stated to play a passive role, and simply to prevent the dental 

 apparatus passing too far backwards. But here also it seems idle to suppose that a very 

 powerful muscle such as the longitudinalis linguae requires any assistance, and still more 

 so that a strand of fatty areolar tissue is capable of arresting its action. The " tongue," 

 of course, passes as far backwards as the anterior mucosa of the mouth and its related 

 skin will allow it, and no further. 



