ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 673 



mechanische Leistung des blasigen Stiitzgewebes nur teilweise jener des echten 

 Knorpelgewebes entspricht. Damit haben wir auch die genetische oder besser 

 gewebsbildende Verwandtscliaft beider Gewebe beriihrt. Dieselbe findet darin ihren 

 Ausdruck, dass gelegentlich Bildungszellen des blasigen Stiitzgewebes sich in echte 

 Knorpelzellen umwandeln konnen." Again (p. 250), he says : " Besonders an ersterer 

 Stelle [tendon of the longitudinalis linguae] handelt es sich also um eine vollstandige 

 Analogie mit den Sesamknotchen in verschiedenen Sehnen bei Anuren und Reptilien 

 und miissen hier diese blasenformigen Zellen der Myxine, wie bei den genannten 

 Tiergruppen, als eigentiimlich metamorphosierte Zellen des fibrosen Gewebes angesehen 

 werden." 



Near the centre of the notochord of Myxine is found usually what is known as the 

 " fibrous core " (ep. fig. 1, Part II.). As discovered by v. Kolliker and v. Ebner, this 

 consists of chordal cells elongated in a longitudinal direction and having relatively 

 thick walls. Schaffer (28, pp. 199-200) draws attention to a somewhat similar 

 structure in the external bar of the anterior segment of the basal plate, in the middle 

 of which exists a mass of ground substance lodging very flattened and modified 

 cartilage cells. This is compared with the fibrous core in the skull chorda of the 

 Ammocoete and in the chorda of the larval eel, and is said to be due to the 

 encroachment of the peripheral chordal cells producing a simplification and compression 

 of the cells in the axis. 



The cranium of Bdellostoma has been described by Miss Julia Worthington (36). 

 It is a tough, flexible capsule of dense fibrous connective tissue lined with endothelial 

 cells, the walls being thinner at the cephalic than at the caudal end. The fibres are 

 very thick and tough, and may be either straight or wavy. "At the hind end of the 

 medulla, ventral to it, and just anterior to the notochord, lying between the layers of 

 the fibrous capsule, is a thick plate of cartilage, connecting the cartilaginous ear 

 capsules. This is the only cartilage found in the cranium." Assuming that this does 

 not refer to the parachordal cartilage, I find no such plate in Myxine, nor, of course, has 

 it anything to do with the infiltrating cartilaginous substance wrongly described in the 

 cranium by J. Muller. The shape and relations of the cranium to the skeleton in 

 Myxine are shown in fig. 1 (cr.). 



As I have stated above, the boundaries of the soft and hard cartilage do not admit 

 of strict definition, although a fundamental pattern unquestionably exists. A com- 

 parison of the figures in my first part with those now given, and also of a number of 

 preparations and series of sections, shows that whilst some regions consist always of 

 hard cartilage and others of soft, there are places again which appear to constitute a 

 kind of neutral ground, and in which the distribution of the two kinds of cartilage 

 certainly varies. Such places are, for example, the hyoid arch (%.), the nasal capsule 

 (n. c), and the hypophysial plate (h. p.). Further, at the numerous places where the 

 two kinds meet, the union is so close and intimate as to knit the skeleton into a 

 connected whole without the presence of joints or sutures. It is useless to speculate 



