1903.] IN THE ‘ CHALLENGER’ COLLECTION, 77 
eine doppelte Linie leuchtender Punkte entlang der iiusseren 
Geissel der Innenfiihler und achtens verlief eine im hinteren 
Teile zusammenhingende, im vorderen in Punkte aufgeloéste Linie 
parallel zum Unterrande des Riickenpanzers.” The arrangement 
of the organs in Acanthephyra pellucida is rather different from 
that in Sergestes challengeri, but it shows yet more resemblance 
to it than to that in the Euphausiide. Both in S. challengeri 
and in A. pellucida an astonishingly high number of organs exist, 
but as to the structure of the organs in the last-named form 
unfortunately nothing is known. I suppose that they are real 
compound organs, not dermal glands as in the Entomostraca. 
If we look for comparison between all luminous animals, it will 
be found that only some deep-sea or pelagic fishes and two 
Cephalopoda of the genus /istioteuthis (according to Verany and 
Joubin) possess a number of real organs which can be compared 
with that found in Serg. challengeri and Acanth. pellucida. 
I have looked for luminous organs in all adult species of 
Sergestes known to me and in Acanthephyr a purpurea A. M.-Kdw., 
but the result was absolutely negative. It is a very curious f: act 
that about 150 very compound organs are found in one species of 
Sergestes, while they seem to be quite absent in all other species 
hitherto known of the genus. It may be added that the luminous 
species does not deviate from some of the other forms in any other 
character of importance: it belongs, even within the genus, to a 
group which contains several deep-sea forms closely allied to each 
other. Considered in this light, the existence in one species of 
about 150 compound organs seems to me a most astonishing 
feature. 
Supplementary Note. 
In the preceding section it has been mentioned that among the 
Cephalopoda two species of MHistioteuthis possess a large number 
of compound luminous organs. My friends Prof. G, “B. Howes 
and Rey. Ph. R. R. Stebbing have very kindly directed my 
attention to two papers, which ‘contain some additional knowledge 
of the same topic and may be quoted here. W. HE. Hoyle (Mem. 
& Proc. of the Manchester Liter. & Philos. Soc. vol. xlvi. part vi. 
1902) points out and describes the structure of twenty-nine 
luminous organs in Plerygioteuthis margaritifera, but this number, 
though rather high, is yet considerably lower than that in 
Ser gestes challengeri. C. Chun (‘ Aus den Tiefen des Weltmeeres,’ 
Jena, 1900) describes and figures (p. 532) the arrangement and 
the colours of twenty- four laemaous organs 1 * Enoplotenthis 
diadema Ch., n. sp.” Furthermore, he writes (pp. 5382-383): 
“ Abnliche, wenn auch etwas kleinere Organe, besetzen bei 
Vertretern der Gattung Calliteuthis die ganze Korperoberfliiche 
von den Armen bis zu den Schwanzflossen. Die Bauchseite ist 
auch hier wieder reichlicher mit ihnen ausgestattet, als die 
Riickenfliiche.” An accompanying figure of a “ Calliteuthis n. sp., 
seen from the ventral side, shows a number of organs considerably 
surpassing that in Serg. challengeri. 
