HOYLE : REPORTS ON THE CErHALOPODA, 00 



1. Tlie Posterior Cup presents an outer coating of brown pigment (c.) which, 

 however, is neither so thick nor so dense as that of the ocular organ. The 

 scales composing the cup (p. c.) are thicker and more closely packed, and the 

 connective tissue lying between them is more delicate. Most of the sections 

 of this organ which I examined had been staii>ed with carmine, and this fact 

 may account for an apparent difference in the composition of the scales. They 

 present a granular appearance, but do not show traces of a network like that 

 described above. The form of the scales, judging by an examination of tan- 

 gential sections, seems to be much less regular than in those above mentioned. 

 They give off processes which branch, and in some cases almost appear as 

 though they joined one scale with another, though I hardly think that such is 

 the case. A somewhat oblique section, through the cup and the central kuub, 

 is shown in Fig. 8, and exhibits very clearly the concentric arrangement of the 

 scales round the central knob. 



2. TJie Inner Cone (i. c.) presents very little difference from that of the 

 ocular organs except that the fibres composing it are more delicate. In some 

 of the sections, they show a tendency to curve round the outside edge of the 

 central mass, but this appearance I imagine is due to the sections not being 

 cut exactly through the centre. In some places I detected a nerve passing 

 through the inner cone in the same way as in the ocular organ. 



3. The Central Mass (c. m.) is in general form intermediate between that 

 of the ocular organs just described and that of P. margaritifera. It resembles 

 the latter in the fact that it has no scales in its centre, and that it does not 

 show distinct cell outlines, whilst in the fact that it extends as far as the rim 

 of the inner cone it presents a likeness to P. giardi. It is made up of finely 

 granular substance which stains only very faintly. The nuclei are very few 

 and far between in the central knob, but are much more abundant towards 

 the base of the conical portion, where many of them seem to be elongated in 

 the direction parallel to the base of the cone. 



4. Hie Anterior Cap (a.c, a.c/) is made up of two laj^ers of about equal thick- 

 ness, but whereas in the ocular organs the deeper layer is composed of delicate 

 fibrils and the more superficial of large scales, in this instance the scides are in the 

 deeper part, whilst the fibrous portion is above. The scales differ from those of 

 the posterior cup inasmuch as they show a marked tendency to become resolveil 

 into fibres (Fig. 7). One or two of the larger ones, however, show no fibres, 

 but simply a granular structure similar to those of the posterior cup, but more 

 pronounced. The superficial layer is almost homogeneous, but there can be 

 seen in it delicate striations which run for the most part parallel with the sur- 

 face. They are more clearly marked and less wavy in the deeper layers. 

 The nuclei are fairly abundant and are fusiform in shape, with their long axes 

 parallel to the direction of the fibres. 



5. The Collar (ro.) is the structure whose presence most clearly distin- 

 guishes the siphonal from the ocular organs. It surrounds the organ parallel 

 with its equator just opposite to the deeper layer of the anterior c^p. It is 

 covered by the connective tissue capsule of the organ and in minute structure 



