HOYLE : llEPOKTS ON THE CErHALOPODA. 57 



its deeper surface. It consists of a single layer of cells each with a definite 

 rounded nucleus, ep. The pigment is of the retldish-brown character, which liiis 

 already been described in speaking of the siphonal and ocular organs and 

 appears to be contained in the inner portion of the cells {p. I.) 



IV. The Abdominal Organs (Plate 9, Fig. 1, A^, A\) are two in number. 

 Tlie anterior (^1^) occupies the position of the three organs in P. niargaritifera 

 (Hoyle, : 02, Fig. 1, A 1, 2, 3), though it is proportionately not quite so Jar 

 in front of the branchial organs as it is in that species. The posterior one 

 (Fig. 1, A^) corresponds in position with that marked J. ^J in the figure of P. 

 margaritifera just cited. 



Th,e anterior oi'gan is slightly elliptical in a superficial view with the longer 

 axis transversely ; its axes measure 0.6 and 0.4 mm. respectively. The organ 

 is nearly hemispherical (or more accurately henu-ellipsoidal) embedded in the 

 tissues, with its flat surface outwards and on tlie same level as the abdominal 

 wall. On the anterior aspect a kind of thread or stalk runs from it, em- 

 bedded in the tissues. One organ which I removed was cut into sections 

 longitudinally, that is, by planes parallel to the sagittal plane of the body 

 (Fig. 12) ; an examination of these showed it to be composed of the following 



structures ; — 



1. The Capsule. 



2. The Pigment Layer. 



3. The Cup. 



4. The Inner Cone. 



5. The Central Mass. 



6. The Cover. 



7. The Superficial Connective Tissue. 



1. T]ie Capsule of connective tissue (c.) covers the whole of the hemispherical 

 surface of the organ ; it is very thin (about 0.08 mm. thick) and almost 

 structureless, though delicate fibres can be traced here and there, and a few 

 nuclei are scattered in it. 



2. The Pigment Lager (p.) inmiediately within the connective tissue just 

 mentioned is thickest just opposite to the stalk and made up of reddish-brown 

 granules like tlie similar layers iu the other organs. 



3. The Cup (p. c.) is made up of scales, so far as can be made out closely 

 resembling those already described in other organs. The only jtections I have 

 of this organ are so deeply stained with braziline that it is impossible to make 

 out any structure in them. This coat is on average 0.1 mm. thick. 



4. The Inner Cone (r. c) can be made out distinctly only on that si<le of the 

 organ turned towards the stalk. It consists as in other cases of thin wavy 

 fi!)res very deejjly stained. It is much thinner and less conspicuous in this 

 instance than in the others. 



5. The Central Mass (r. m.) is much less regular in shajie tlian in those ciises 

 already described, but shows traces of a constriction indicating a division into 

 a deeper portion ami a more superficial corresponding respectively to the splie- 

 roidal and conical portions of other cases. The minute structure is very badly 



