ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 707 



xamination of a series of vertical longitudinal sections shows that this is true only in 

 i limited sense. The superficial fibres of the tendon pass respectively over the dorsal 

 md ventral surfaces of the dental plate, across the fenestras, and are ultimately 

 continuous with the corresponding fibres of the tendon of the retractor muscle. They 

 do not constitute the whole of the fibrous tissue crossing the fenestrse, nor is the soft 

 pseudo-cartilage of the tendons prolonged beyond the particular cartilage into which 

 each is inserted, except to a slight extent in the case of the longitudinalis linguae. It 

 in fact amounts to nothing more than that there is a fusion (of course inevitable) 

 between the tendons and the fibrous sheath of the dental plate. 



We may now conveniently review the function of the two protractor muscles of the 

 dental apparatus, but we must first consider the very curious habit on the part of the 

 living Hag of entirely protruding its dental plates when either disturbed or stimulated. 

 When a Hag is placed in a quantity of some fixing solution, say formalin, it does not 

 die for some time, but swims rapidly about, showing its teeth or snarling in what is 

 certainly an alarming manner. This is effected by bringing the dental apparatus 

 forwards and then rotating it on its anterior border round the ventral margin of the 

 mouth through an angle of about 115°. The result is that the dental plates, which, 

 when withdrawn, look upwards, with the teeth pointing backwards, now look forwards 

 and somewhat downwards, with the teeth pointing anteriorly. I have succeeded in 

 preserving several specimens with the plates extruded, but do not figure them, as satis- 

 factory figures have already been published by P. Furbringer and Ayers. This 

 interesting and unique phenomenon was first figured for Myxine by Gunner in 1763, 

 and described by him in the following words : # " Am schonsten liess es, wenn er 

 anting seine Kiefer aus beiden Seiten hervorzuschieben und zwo Eeihen kleiner 

 gelber Zahne herzuweisen, die zugleich mit dem Zahnfleisch sehr genau wie zwcen 

 kleine und sehr feine gelbe Kamme anzusehen waren. Wenn er diese seinen 

 gelben Zahne zum Vorschein brachte, so liess es fast ebenso, als wenn man einen 

 Spiegel oder einen Schrank mit zwo halben Thieren offhet, also dass jede Thiire auf 

 ihre Seite fallt." 



J. Muller, in 1836, severely criticises this passage without, it must be confessed, 

 clearly understanding it, and asserts that it is "ganz unrichtig." His reasons are negatived, 

 partly by erroneous anatomical observation, and partly by his failure to realise that the 

 "tongue" and mucosa are one, and therefore must both move together. In 1873 

 Gunner's observations were confirmed by W. Muller (as reported by P. Furbringer) 

 on living material of Myxine, and some were killed in spirit with the dental plates 

 everted. According to W. Muller, the action is very rapid and powerful, and is 

 accompanied by a peculiar noise. In 1874-5 P. Furbringer {op. cit.), working with 

 W. Muller's material, published two figures of the everted dental apparatus, and gave 



* See the German translation from the Danish, Drontheim Ges. Schrift., ii. p. 230, 1765. 

 TRANS. ROY. SOC. EDIN., VOL. XLV. PART III. (NO. 26). 101 



