NA TURE 



[Dfxember 9, 1922 



a scale never previously attained, and later was instru- 

 mental in establishing the origin of trench fever and 

 its transmission by lice. 



Sylvester Medal. Prof. Tullio Levi-Civita. — 

 The investigations by Levi-Civita in pure geometry 

 were the necessary foundations for the important 

 physical discoveries of Einstein and Weyl. Levi- 

 Civita has also shown himself one cd the most fertile 

 and original of investigators in differential geometry 

 and theoretical mechanics. 



Hughes Medal. Dr. Francis William Aston. — 

 Dr. Aston, by the use of an ingenious method of 

 focussing positive rays, has shown that a large 

 number of the elements are complexes consisting of 

 two or more kinds of atoms, having identical chemical 

 properties but differing in atomic weight by one or 

 more units. Except in the single instance of hydrogen 

 the atomic weight of each constituent is, to the limit 

 of accuracy, a whole number on the basis of oxygen 

 -16. 



Live Specimens of Spirula. 



By Dr. Johs. Schmidt, Leader of 



UEW animals have been of more interest to 

 •*■ zoologists than the little cuttle-fish Spirula. 

 Related to the extinct Belemnites, and characterised 

 by having an interior, chambered shell, it occupies 

 an isolated position among recent species. Dead 

 shells (see Fig. 2) are found on the sea-shores 

 particularly of warmer seas, where they may drift 

 ashore in great numbers, but the 

 animal itself has hitherto ranked 

 among the greatest zoological 

 rarities, of which only very few 

 museums possess a specimen. 



On the third Dana expedition 

 we captured considerable num- 

 bers of Spirula in the North 

 Atlantic, and were also fortunate 

 enough to observe many speci- 

 mens alive. I propose then, in 

 the following, to describe some 

 of our observations, throwing 

 light upon the habits and occur- 

 rence of the species. 



Appearance. — The following re- 

 marks apply to living specimens, 

 a point which should be em- 

 phasised, as both colour and 

 shape are often appreciably 

 altered by preservation. The 

 body, or mantle, is shaped like 

 a cylinder cut away abruptly at 

 the back, the head and arms pro- 

 truding from the front part. 

 As seen in Fig. 1, the arms are 

 most often kept close together, as 

 for example when the animal is in 

 motion, giving the anterior part of the body a conical 

 shape. At the hinder end are two fins, roughly semi- 

 circular. Their basal parts are not parallel, but 

 converge toward the ventral side of the animal. 

 The fins can be pointed straight out behind (Fig. 1), 

 or laid flat in against the hinder part (Fig. 2). In 

 the centre of the latter, between the two fins, there is 

 a circular disc (the terminal disc) having in the 

 middle a small bead-like organ. At the outer edge 

 of the disc is a ring of pigment ; otherwise it is 

 colourless. The small central bead is a light organ. 



The colour differs from that of other"' cuttle-fish. 

 The mantle has a peculiar whitish sheen, most re- 

 sembling that of asbestos. A further similarity to 

 the mineral lies in the fact that the surface of the 

 mantle is often somewhat frayed or fluffy. The 

 greater part of the mantle is without pigment ; some 

 colour there is, however, of a rusty red, in a narrow 

 band along the anterior margin of the mantle, 

 •specially on the dorsal side. There is also pigment 

 on the hinder end of the body and at the base of the 

 fins. On touching a live specimen, the rusty colour 

 at the hinder end will often almost disappear, the 

 chromatophores contracting to little dark specks. 



Fig. 1. — Live specimen 

 of Spirula, moving down 

 toward the bottom of the 

 aquarium. While so 

 moving, the head is 

 directed forward (down- 

 ward), the fins at the 

 rear are thrust out ver- 

 tically, and the funnel 

 is turned upward (this 

 last is not visible here, 

 the figure showing the 



About half natn- 

 Photo by K. Stephenseu. 



the Dana Expeditions, Copenhagen. 



Arms and head exhibit the silvery sheen and also 

 pigment, the latter dense and of a rusty brown. 

 The extremities of the arms, however, especially of 

 the two longer ones, are somewhat lighter and lai king 

 pigment. The funnel also is pigmented, but not at 

 its mouth. 



Movements, etc. — The movement of the Spirula is 

 characterised throughout by the presence of the 

 interior, chambered shell, which is situate at the 

 posterior end of the body, and tends to lift this 

 portion in the water. A specimen recently dead, or 

 a live one not inclined to active movement, will 

 therefore, if placed in an aquarium with sea water, 

 rise to the surface, and remain suspended there head 

 di iwnwards, with the lighter, posterior part uppermost. 

 If moved from this position, it will immediately 

 swing back to it again, like a weighted tumbling 

 figure. 



On board the Dana we frequently observed live 

 specimens of Spirula. When taken from the net and 

 placed in an aquarium, they would at first invariably 

 remain suspended at the surface of the water, motion- 

 less, and to all appearance lifeless. As a rule, however, 

 death was only simulated. Left to themselves, they 

 would generally come to life, and soon begin breathing 

 and other movements. The respiratory movements 

 are effected by rhythmical contractions of the mantle, 

 whereby water is forced out through the funnel. 

 As the mouth of this is turned towards the rear — i.e. 

 upwards — the water flows up along the ventral side 

 of the mantle. This vertically ascending current of 

 water is easilv noticeable, from its disturbing the 

 frayed surface of the mantle. 



Like other cuttle-fish, Spirula often makes swift, 



ii'. : I'tvs.-Tvol specimen of Spirula, about 39 mm. long (the head 

 slightly damaged). The shell seen at tic- -I'lc, which has 35 chambers, 

 allows tli,; relative size of the shell in a specimen as illustrated. The animai 

 is seen from the ventral side : the inner shell can be discerned showing 

 through. About natural size. Photo by K. Stephensen. 



jerky movements, dashing off suddenly in any direc- 

 tion : upwards, downwards, or from side to side. 

 I hese rushes were generally made by " backing," 

 the animal moved with its hinder end forward, 

 having first " reversed " the funnel, so as to turn 

 ii opening forward towards the head, at the same 



NO. 277 !, VOL. I io] 



