ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 671 



Similarly, the histogenesis of the soft cartilage at these places resembles that of the 

 gill and tail fin cartilages of Ammoccetes. " An den meisten librigen Stellen lasst die 

 Intercellularsubstanz des weichen Jfyxme-Knorpels, wie ich schon an andrer Stelle 

 bemerkt habe, zweifellos eine Zusammensetzung ans interterritorialer Grundsubstanz 

 (primarer Kittsubstanz) und sekundar eingelagerten Zellhofen . (Kapselsubstanz) 

 erkennen. Trotzdem bleibt die gesamte Intercellularsubstanz stets sparlicher als im 

 harten Knorpel und stellt dieselbe — mit Ausnahme der ebengenannten Stellen — ■ 

 vielfach ein Balkenwerk mit polygonalen Maschen dar" (p. 229). Elsewhere, Schaffer 

 remarks that there occurs in the soft cartilage a true " interterritorial " substance, as 

 in the hard cartilage. 



Schaffer concludes his description of the soft cartilage with a discussion of the 

 relationship between the soft cartilage and the hard. Can the soft cartilage pass over 

 into the hard — must the hard pass through a soft stage, or is the hard cartilage from 

 the beginning a separate and independent type of tissue ? In Ammoccetes Schaffer 

 repeats that the two kinds are not related, and that their points of junction are only 

 secondary. In the Myxinoids the question is a more complex one, since the shuffling 

 of the two kinds is much more in evidence, and, if independent, then the skeleton of 

 the Myxinoids must consist of a greater number of originally separate elements than 

 that of the Lampreys. It seems at first sight superfluous to argue about a matter 

 which can only be definitely settled by a study of the development of the Myxinoid 

 skeleton. Schaffer, however, definitely ranges himself against Studnicka, who 

 regards the distinction between hard and soft cartilage as an artificial one, and holds, 

 on the strength of the Ammoccete, that the two kinds represent originally independent 

 types of tissue. He says that though the soft cartilage of Myxine may micro- 

 chemically and morphologically approximate to the hard, it is not transformed into it, 

 and further that typical hard cartilage is distinctly separated by certain morphological 

 peculiarities from the hard variety of the soft cartilage. Again, he refers to the 

 sporadic occurrence of nests of cartilage in places where they can only represent a 

 degenerating structure, and mentions one such between the second and third gills 

 which consisted of a nodule of hard cartilage embedded in pseudo-cartilage. The 

 point here seems to be that the nodule should have reverted to the soft stage if it had 

 ever passed through it phylogenetically. 



It appears to me hardly profitable, in the absence of embryological data, to enter 

 into any discussion of Schaffer's views on the above question. I should like, however, 

 to draw attention to one or two facts. It is unquestionably true that a broad funda- 

 mental pattern may be discerned in the distribution of the hard and soft cartilage, but 

 it is also and equally true that that pattern does not depend on any sharply defined 

 topographical distinction between these two tissues. For example, the anterior half of 

 the forward rod of the hypophysial plate was, in the large old 45^ cm. Myxine on 

 which my previous drawings of the skeleton were based, formed of hard cartilage. In 

 young animals it consists entirely of soft cartilage, and in the 25 cm. Hag of my 



