12 



CARL CHUN. 



[REP. OF THE "MICHAEL SARS" NORTH 



and as yet not very prominent. The fins are now larger. 

 Their bases measure 2 mm., slanting dorsally in front 

 and ventrally behind. The fins, 3 mm broad, do not 

 yet overlap the posterior end of the body. The pigmenta- 

 tion of the mantle has advanced, the edge of the mantle 

 and the posterior end of the body being intensely coloured. 

 The intermediate part of the mantle seems to be poorly 

 pigmented, but it had only in part been preserved in the 

 case of one of the older stages. In the other cases it 

 had been to some extent damaged, the silvered layer of 

 the cutis appearing on the surface of the specimens. The 

 shape of the posterior part of the body is further of 

 particular interest (pi. II, fig. 3). Being light-coloured it 

 is sharply distinguished from the intensely pigmented 

 parts surrounding it, and in its centre we notice for the 

 first time traces of a white conical structure, which I have 

 attempted to explain as being a light-organ, surrounded 

 by a hardly perceptible thickening. Although the specimen 

 has been somewhat damaged, the chambers are not laid 

 open but are covered by a thin membrane. The thick- 

 ening of the mantle having now increased about the 

 shell, the ovals provided with a thin membrane are more 

 sharply defined. On the head the greatly enlarged eyes 

 are conspicuous. They may be seen from the side above 

 the edge of the mantle, and are almost entirely covered 

 by the nearly closed fold of the lid. The diameter of the 

 eyes would be at least 2 mm. The arms show a more 

 powerful development than in earlier stages, but are still 

 devoid of strong pigment like that characterising the other 

 parts of the head. 



As regards the other young specimens of Spirilla, 

 their shape gradually approaches to that of the adult 

 animal. The club-section of the tentacles protrudes only 

 a little, one might almost say timidly, among the arms. 

 The eyes increase in size and the formation of angles 

 in the mantle becomes more marked, the ventral ones 

 commencing to enclose the funnel. Above all the posterior 

 part is approaching its final development. The whitish 

 cone of the light-organ becomes more sharply defined, 

 and is surrounded by the thickened pigmentless moulding, 

 the lips of the latter surrounding the light-organ and 

 forming a faintly pit-shaped depression. Pigment has been 

 intensely developed around the light-coloured pole and 

 has been distributed dorsally as well as ventrally over the 

 chambers of the shell. The pigment is almost as vigorous 

 on the bases of the fins, which until now have been 

 devoid of pigment. I wish finally to give prominence to 

 the fact that the pit-shaped depression around the light- 

 organ at the posterior end of the body becomes more 

 and more conspicuous during development, and also 

 that folds on the arms become visible, and the tentacles 

 protrude more, as the animals grow up. What has been 



said above would in the main characterise the peculiarities 

 exhibited by the young Spirilla. 



There is, however, one point which i should like to 

 discuss a little further, a point specially emphasised in 

 my description of the adult Spirilla taken by the "Valdivia", 

 viz. that the shell is never left bare on the dorsal or ventral 

 side. In all the specimens of Spirilla I find the shell 

 covered by the thin mantle in the region of the so-called 

 ovals. Only in the oldest specimen, the mantle of which 

 was damaged, the chambers are now and again bared, 

 but we recognise the frayed edge of the membrane round 

 the bared chambers, and we may convince ourselves 

 beyond doubt that we have to do with a damaging of 

 this frail structure. Joubin in his description of the 

 youngest larva still starts from the presumption that the 

 chambers are normally uncovered; he attempts to explain 

 this in quite another — and to my mind much more satis- 

 factory—manner, than Pelseneer did. But since I have 

 been able to show that in the fullgrown Spirilla the 

 chambers are never bare, one may dismiss the idea, that 

 Spirula has an exterior shell. As regards the structure 

 and development of this shell I intend to give a more 

 detailed account in a future publication. 



I may finally mention that in all those specimens 

 where the mantle is damaged, and especially in the cases 

 where the silvery layer of the cutis has been rubbed off, 

 a reticular division of the muscular surface is visible, 

 which is, however, plainly visible only in the case of the 

 two oldest specimens, while in the young stages it appears 

 rather as a fine granulation. I therefore once more declare 

 myself opposed to the attempts at establishing a separate 

 species viz.: Spirilla reticulata, the said reticulation being 

 a character common to all representatives of the genus, 

 and appearing only on the surface of damaged specimens. 



Sepfolidae Tryon. 

 Heteroteuthis dispar Riippell 1845. 

 Stat. 42. 200 m. w. 8 young specimens. 

 „ 56. 100 — 300 m. w. 3 larvae. 

 „ 58. 100 about 20 young specimens, the 



largest one among these — a male 

 — possessing somewhat enlarged 

 suckers on the third arm. 



Sepiola Rondeleti d'Orbigny 1839. 

 Stat. 39 B. Trawl 292 m. 1 specimen. 

 „ 96. 200 m. w. 3 specimens. 



Rossia Caroli Joubin. 

 Rossia Caroli Joubin 1902, M<im. Soc. Zool. France p. 135, 

 fig. 34, 35. 



Fischer et Joubin Exp. Travailleur et Talisman 

 1906, p. 331, pi. XXIV, figs. 3—8. 



