LIGHT PRODUCTION IN CEPHALOPODS. 165 



features. The possible utility of this peculiar development of 

 the function, so far as Heteroteuthis is concerned, is the subject 

 of some interesting speculation in one of Meyer's subsequent 

 papers (:o8, pp. 507-508), which will receive more attention 

 later on. 



We are now brought to a consideration of some important 

 recent work performed by various Japanese observers in con- 

 tinuation of Watases pioneer studies on Watasenia scintillans 

 (Sasaki, :i2, 113, :i4; Ishikawa, :i3). This constitutes probably 

 the chief work which has been done in this field, and therefore 

 merits consideration in considerable detail. 



"In the region where the squids live, that is, in the waters 

 of Namerikawa on the coast of the Japan Sea," writes Ishikawa 

 (:i3, pp. 167-169), "this circumstance [the luminosity of the tips 

 of the ventral arms described by Watase] had already long been 

 known ; but none of our zoologists were aware of it until Watase 

 by chance made the discovery. At a time when he was engaged 

 in the study of fireflies, he was apprised by a schoolmaster that 

 there occurred a species of squid in the sea at Namerikawa which 

 lighted very strongly. Pursuant to this suggestion he sought 

 the village named, found in due course a species of small squid 

 with powerful light organs, and recognized the same as a species 

 of Abraliopsis. As he has orally told me, it was on the 28th 

 of May, 1905, on the memorable day of the battle of Tsusima, 

 hat he saw the light of this squid for the first tim2 



"The large swellings at the tips of the ventral arms, as well 

 as two or three smaller dots, are, as he remarks, luminous organs 

 of the first order. They shine so brilliantly that when one 

 observes the animals in dark water, one sees only two effulgent 

 bodies moving in the dark water, like the glow of an electric 

 contact, and the lively oscillations of the invisible arms produce 

 a very wierd effect. Next to these in the intensity of their light are 

 the eye organs, and then come the remaining organs. The 

 three types of organs do not always shine simultaneously; often 

 only one or the other. But it can also happen that the animal sets 

 all the organs into action at the same time. When the mantle 

 organs light up, the form of the animal springs out spectre-like in 

 the dark water. These organs, arranged in rows, when one 



