45^ 



NA TURE 



[August 29, 1907 



tion of the stem of the tentacle for about 2 mm. of its 

 length is occupied by a large rounded cell-mass whose 

 diameter is more than half that of the tentacle. The 

 nerve which usually occupies this position is pushed to 

 one side and flattened out like a ribband. .Most curious 

 is the fact that on the side opposite to the nerve a second 

 organ is superposed on the first, which is of more complex 

 structure, inasmuch as it has in its centre a mass cl 

 photogenic cells surrounded by a system of radiating fibrils 

 with a pigment layer and tapetum at one side (see I'ig. j 



(ii.) As an example of the complex organs we may con- 

 veniently take those of Histioteuthis rUppelli, where 

 they are scattered over the ventral surface of the mantle, 

 siphon, head, and arms, forming in particular a definite 

 ring round the ventral half of the margin of the ocular 

 aperture. The organ itself is an ovoid body, about i mm. 

 in length and somewhat less in diameter. The deeper 

 three-fourths of this cup are covered with a thin layer of 

 pigment, which is lined with a thick coating made up of 

 small lenticular bodies packed closely together and forming 

 a kind of mirror. The space within this, equal in diameter 



1. — Semi-diagrammat'c sections of typ'.cal luminous organs :- 

 gioteuthh ^ardi B, Tentacular organ- of Tlmimatolitmpas, C, Pall 

 D, PalHal organ 0^ llislioteulhis rtippclli. a. Accessory lentacular orgai 

 r/, Diaphragm. /, Lens, ifa, Lacuna. «/, Mirror (external). «, Nerve. 

 genie cells, //j', Photogenic cells of accessory organ, r, Reflector (inte 



to about half the diameter of the organ, is filled with a 

 mass of large deeply staining cells with large distinct nuclei. 

 The more superficial portion of the organ is made up of 

 what seem to be refractive structures. The deeper portion 

 is conical, fitting into a hollow in the photogenic mass, 

 whilst the upper part is bounded by a definite convex sur- 

 face, the function of which is obviously lenticular. Nerves 

 have been traced passing through the mirror to the light- 

 prodi^cing cells in the centre. This ovoid body is situated 

 at the posterior end of a somewhat hollowed patch of 

 an elongated oval shape, which may measure as much as 

 10-12 min. in its antero-posterior diameter. A consideration 

 of the form and position of this hollow-cd patch and of its 

 relation to the axis of the organ shows pretiv clearly that 

 it is an external mirror, destined to throw the rays of light 

 downwards and forwards (see Fig. d). 



_ One of the inost coinplicated organs known is that found 

 in the marile of AhraUo^sis. Here the whole apparatus 

 IS spheroidal in form and surrounded bv a black coating, 

 derived apparently from a number of confluent chromato- 



phores. The photogenic cells lie rather in front of the 

 centre, and before them again a ring of black cells seems 

 to discharge the functions of an iris diaphragm. Behind 

 the source of light is a reflector consisting of two parts : 

 the deeper is concave, spheroidal, and made up of numerous 

 concentric layers; the more superficial portion is conical, 

 and also composed of concentric lamellae. Partly in front 

 of and partly behind the diaphragm is a lenticular mass of 

 tissue. These little lanterns are scattered in considerable 

 numbers over the ventral surf.^ce of the mantle, funnel, 

 head, and arms, and the appearance of the animal when 

 they are functionally active must be brilliant in the extreme 

 (see Fig. c). 



If we examine the organs just described and the others 

 above enumerated, we sec that certain conditions are ful- 

 filled in all cases — namely, the presence of a mass of deeply 

 staining, active cells with distinct nuclei, supplied with 

 blood-vessels and ni^rves. These, then, are the essential 

 parts of the apparatus, though even here differences obtain : 

 for example, in Thaiinuiloliwipas the cells are polyhedral, 

 highly refrac'.ile, and clearly defined, with spheric.il nuclei 

 and distinct nucleoli. In Chirotcu- 

 thopsis the cells are few and large, 

 and partially fuse one with another. 

 In Pterygioteiithis the fusion has pro- 

 ceeded so far that the cell-boundaries 

 are no longer recognisable, and there is 

 present a finely granular mass in 

 which numerous nuclei of varying size 

 may be distinguished. In other cases 

 the cells branch out into fibres and 

 form a reticulate structure (Calli- 

 teuthis). In rare cases, as, for 

 instance, the tentacular organ of 

 Thaumatolampas, above described, this 

 essential part constitutes the whole 

 organ ; but generally other structures 

 are superadded, such as a pigment 

 coat, reflector (" tapetuin " of Chun), 

 !<'ns, :ind diaphragm, as has been 

 mentioned in the complex organs just 

 described. 



Numerous interesting questions at 

 once suggest themselves in regard to 

 these structures, and it is very dis- 

 appointing to admit that in regard to 

 , almost every one the answer is a con- 



A*^ fcssion of ignorance. 



The first inquiry is : What is ihe 

 origin of these organs, and from what 

 primitive structures are they evolved' 

 Here it is possible to say but little ; 

 there is no instance in which the 

 development of these organs in the 

 embryo has as yet been studied. A 

 larva, believed to be that of Histio- 

 teuthis, came into my hands a short 

 time ago, and full of hope I had a 

 portion of the mantle cut into sections, 

 but with no result whatever ; there was 

 ould interpret as the rudiment of such 



nchial organs of Ptcry- 

 i il organ of Abralio/isis. 

 n. c/i, Chromatophores. 

 p. Pigment. ///, Photo- 



NO. 1974, VOL. 76] 



nothing which 

 an organ. 



Those organs occur in so many and such scattered families 

 that it seems clear they must be polyphyletic. Further- 

 more, even in one and the same species the different organs 

 are not all constructed on the same plan. In Abraliopsis, 

 for example, the pallial organs are quite different from the 

 ocular ; but the most striking example of this sort of 

 complexity is found in the remarkable Thaumatolampas, 

 which has altogether twenty-two organs constructed on no 

 fewer than ten dilTercnt principles. It seems difficult in 

 such a case to resist the conclusion that these organs have 

 been separately evolved at different times, and perhaps from 

 different origins, during the phylogenetic history of the 

 species. 



This variety in the structure of these organs naturally 

 suggests the query : Do these differently designed lamps 

 give out different kinds of lights? Here we have the 

 observation of Prof. Chun on board the ^'aldivia to 

 guide us, according to which in the living animal the middle 



