178 S. STILLMAN BERRY. 



in both genera relatively enormous, head is produced, which would 

 seem to render it a physical impossibility for the animal to propel 

 itself in a straight path without recourse to spiral movement or 

 some violent sort of counter twisting. This asymmetry extends 

 quite inexplicably to the photogenic organs, inasmuch as the 

 "normal" right eye has a well developed circlet of photophores 

 surrounding the lid opening as above described, while the Brobding 

 nagian left eye has the photophores of its circlet not only pulled 

 farther apart by the distention of the lid, but its every component 

 reduced almost to a rudiment, some of them quite atrophied, 

 or they may even be, as Sasaki has stated for Calliteuthis sep- 

 arata, 15 absent entirely. It seems as though from the very 

 nature of the case there must be some correlation between such 

 pronounced asymmetry and the habits of the animals, but no 

 reasonable explanation of what might be necessary to bring 

 about or to render advantageous such an anomalous condition 

 seems ever to have been suggested. In Mastigoteuthis glaukopis 

 there is no circumocular circlet of photophores, but a single 

 photogenic organ is described as occurring in the ventral edge of 

 each lid sinus. 



In a few species the integumentaty photophores are few and 

 consequently definite in number and position (Ancistrocheirus, 

 Thelidioteuthis, Hyaloteuthis , Eucleoteuthis) . This is probably 

 true also of the very young or larval stages of all the species 

 possessing photogenic organs, but in adults of most species, 

 though still continuing to retain more or less evidence of the 

 primal bilateral symmetry, they are apt to increase to such an 

 extent as to become practically or quite impossible of separate 

 identification and enumeration and thereupon show little con- 

 stancy in either number or position. 



Eucleoteuthis is a genus which deserves discussion by itself. 

 It is unique among known cephalopods in that its photogenic 

 organs instead of forming small rounded or ovoid capsules as in 

 practically all the other genera, are developed as a pair of narrow, 

 more or less interrupted stripes or bands of photogenic tissue 

 extending along the ventral aspect of the mantle for nearly its 

 entire length. A small oval tract of similar tissue flanks the 



16 Journal College Agriculture Tohoku Imperial University, V. 6, p. 137, 1915. 



