678 PROFESSOR FRANK J. COLE 



probable, that Schaffer really has in his mind the same muscle as Ayers and Jackson, 

 there seems, as I formerly thought (7, p. 756), some reason for this view. The muscle 

 and the third segment certainly appear to be merely parts of one whole, but an 

 intimate examination of the muscle is entirely against this assumption. The mere fact 

 that the copulo-copularis is a transverse constrictor muscle, of course without a tendon, 

 is in itself sufficient, since I take it that no conversion of muscle fibre into pseudo- 

 cartilage is asserted. There is, in fact, no evidence to show that the muscle was ever 

 more extensive than it is now, and we must therefore question Ayers and Jackson's 

 suggestion until it is better supported. 



The dental apparatus is regarded by Ayers and Jackson, not as a tongue, but as 

 the detached lower jaws. Schaffer, in his latest paper, dissents from this view, and 

 compares it with the tongue of the eel and the hyoid bone of Amphibia. He therefore 

 approves of the old view that the structure is a tongue. The basal plate he regards as 

 a strongly modified lower-jaw apparatus (Meckel's cartilage). Since Schaffer's paper 

 was published, Stockard has provided us with some evidence on this question. 

 From a study of the development of the visceral clefts, Stockard decides in favour of 

 Ayers and Jackson, and the view therefore now rests on something more than 

 conjecture. Unfortunately, Stockard does not describe the development of the 

 skeleton of this region, and it is to be hoped that he will complete the case by a 

 description of the skeletal parts of his embryos at an early date. 



Schaffer's recent description of the dental apparatus agrees largely with mine. 

 He does not, however, mention the small foramen of the anterior arch (a. d. p.), nor 

 the posterior external process of the same (a. d. p.'). The posterior arch (p. d. p.) he 

 figures as composed of hard cartilage, but with a small cylinder of soft cartilage at 

 its centre (cp. 7, fig. 7). In my sections only the posterior narrow part of the 

 posterior arch, i.e. just where it fused with the anterior arch, consisted of hard cartilage. 

 The rest of the bar was formed of soft cartilage, with, however, in the stouter parts, a 

 fairly considerable infiltration of hard cartilage (fig. 1). Another point of difference 

 is that Schaffer finds the whole of the space between the anterior and posterior arches 

 occupied by pseudo-cartilage, whereas I find only a slight deposit there. Both the pro- 

 tractor and retractor tendons, as each approaches its respective arch, are invaded by 

 soft pseudo-cartilage, and in the latter case there are nests of soft cartilage also. The 

 skeleton of the dental apparatus may therefore be sesamoidal. 



The only point I wish to add to my previous description of the skeleton of the 

 velum or pharyngeal valve relates to the external lateral velar bar (e. I. b.). The head 

 of this rod is formed of hard cartilage, and is connected by a bridge of soft cartilage 

 with the inferior process of the pterygo-quadrate where the latter fuses with the hyoid 

 arch. In the sections, however, the opposite angle of the head was formed of soft 

 cartilage, and as this was present on both sides it seems something more than the 

 sporadic occurrence of a small tract of soft cartilage (cp. figs. 1 and 2). 



At the posterior end of the inferior chondroidal bar, and above it, there is a small 



