lOg FESTSKRIFT FÜR LILLJEBORG 12 



this tissue. The nuclei arc ovoid in shape, sometimes a little elongate. The matrix 

 is not so richly developed and not homogeneous as in the true cartilage of the Ce- 

 phalopods, but rather fibrous or lamellous and also chemically different as it is stained 

 by haematoxylin. It may be regarded as having a relation to the true hyaline carti- 

 laee similar to that of the fibrous cartilage of the vertebrates. The thickness of the 

 lamella of the hemichondroid tissue is about one third of that of the lip, but it lies 

 much nearer the external than the internal surface. Towards the periphery of tin 

 lip this lamella becomes thicker, but its substance is not so dense and not so darkly 

 stained, so that it gradually passes over into the other common cellular connective 

 tissue of which it is a modification. On both sides of this lamella the connective 

 tissue of the lip is loose and cellular, with the cellules imbedded in a soft matrix 

 which is not stained by haematoxylin. There are no muscles to be seen in the lip, 

 and thus the aperture cannot be dilated or contracted, but the lip is comparatively 

 stiff and immovable owing to the hemichondroid lamella and seems therefore to have 

 a protecting function. In the centre of the "aboral fossa" we find the "terminal pa- 

 pilla", the base of which "is formed by a lenticular body" as Pelseneer says. But 

 this lenticular body is not in our specimen "of fibrous tissue", and not like the figures 

 given by Huxley (1. c. PI. VI, fig 15 & 16). Its structure is very peculiar and almost 

 as difficult to describe as to explain. The lenticular body is surrounded by a capsule 

 of dense fibrous and reticular connective tissue with its elements (nuclei, meshes etc.) 

 tangentially stretched. At the periphery of the lenticular body this fibrous capsule 

 extends into a layer and can be followed deep into the dense irregular fibrous 

 tissue of the terminal disk. At this continuation of the lenticular capsule strong 

 muscles insert themselves and run obliquely in an oral and centripetal direction to- 

 wards the inner surface of the terminal disk that covers the shell. Of these muscles 

 those mar the periphery run nearly straight from the continuation of the lenticular 

 capsule towards the interior surface of the terminal disk, where, richly ramified, they 

 insert themselves in the connective tissue. The more central muscles, that lie nearer 

 the lenticular body, turn more and more, the closer they lie to the lenticular body, 

 in a centripetal direction and extend towards the oral side of the lenticular body, be- 

 tween that and the shell. I do not think that they cross over from one side to the 

 other, but they extend so far that they partly meet, although not in the centre of the 

 oral side of the lenticular body. The structure of these muscles is similar to that of 

 the circular muscles of the pallium. In young muscles one can see the oval nucleus 

 surrounded by plasma, but in the older ones this is reduced and the nucleus is very 

 elongate and cylindrical. These muscles correspond to those which Pelseneer says 

 radiate, "in front of the lenticular body, from the centre to the periphery". When 



