LIGHT PRODUCTION IN CEPHALOPODS. 179 



outer side of each band at its anterior end, and, in the type 

 species at least, there is a pair of somewhat larger, transversely 

 ovoid photogenic areas on the head at the base of each ventral 

 arms. That these curious tracts should be classified with the 

 remaining organs here collectively referred to as integumentary 

 is by no means certain. 



The arms are a favored situation for photogenic organs. 

 The extension along their outer surfaces of the ordinary inte- 

 gumentary photophores in the case of such genera as Enoploteu- 

 this, Abralia, Abraliopsis, Watasenia, Callileuthis, Histioteuthis , 

 and certain forms of Mastigoteuthis, has already been noted. 

 In addition to this certain special types of organs are sometimes 

 developed. One of the generic characters of Chiroteuthis is the 

 presence of a series of conspicuous dark photophores along the 

 oral aspect of each of the greatly enlarged ventral arms. Nemato- 

 lampas has a small dark photophore embedded in the extreme 

 tip of each arm of the two dorsal pairs. Not only this but each 

 arm of the third pair bears immersed in its tissues along the outer 

 margin a series of plainly visible photogenic organs which con- 

 tinue as the principal component of a long, chain-like, filamentous 

 extension of the arm which in life must extend like a string of 

 fiery beads far in advance of the animal. There are in excess 

 of thirty individual organs in each chain, but the true number 

 may be much greater as no specimens of the species still retaining 

 these extraordinary structures entirely in their pristine state have 

 yet been captured. In Abraliopsis and Watasenia, genera so 

 closely allied to one another that one could with about equal 

 ease be regarded as but a subgenus of the other, there are three 

 large, black, bead-like photophores, with perhaps some smaller, 

 more rudimentary ones, in close juxtaposition at the tips of each 

 ventral arm. As previously related, these are known to give 

 forth a brilliant light. Rudiments of similar organs corres- 

 pondingly situated are known in at least one species of Abralia, 

 another nearly related genus. This is A. astrolineata Berry of 

 the Kermadec Islands. The curious deep-sea Benthoteuthis 

 has a single photophore on the outer periphery of each arm of the 

 three dorsal pairs near the base, and none elsewhere on the body, 

 an arrangement wholly unlike that.met with in any other cepha- 

 lopod. 



