LIGHT PRODUCTION IN CEPHALOPODS. 187 



exception to this rule (see Table VII.). Those species showing 

 the richest development of structural type in general are the ones 

 which depend upon intrapallial rather than integumentary organs 

 to serve the light producing function. Here there is sufficient 

 divergence among the various organs as to discourage almost at a 

 glance any attempt to homologize them on the basis of reference 

 to a single primal type. Not only their diversity, but their 

 extremely sporadic appearance in connection with organs and 

 tissues of heterogeneous origin, is strongly inhibitive of any such 

 view. 



TABLE VI. 



POLYMORPHISM IN CEPHALOPOD PHOTOPHORES. 



I. Genera with Isomorphic Photophores. 



Thelidiotenthis Integumentary. 



Histioteuthis 



Callitenthis 



Benthoteuthis On arms. 



Mastigoteuthis Integumentary. 



Cranchia Subocular. 18 



Liocranchia Subocular. 



Pyrgopsis 



Hensenioteuthis 



Bathothanma 



II. Genera with Dimorphic Photophores. 



Enoploteuthis Integumentary: subocular. 



Leachia Subocular. 



Megalocranchia 



Crystalloteuthis 



Toxeuma 



Taonidium 



Corynomma Subocular (?); intrapallial. 



III. Genera with Trimorphic Photophores. 



Abralia (except .4. astrolineata') Integumentary; subocular (latter di- 

 morphic). 

 Chirotenthis On ventral arms; subocular; intrapallial. 



IV . Genera with Polymorphic Photophores. 



Lycoteuthis In tentacles; subocular; intrapallial; 10 



types (13 if 3 types of accessory organs are 

 counted separately). 



Nematolampas In arms; in tentacles; subocular; intra- 

 pallial; at tip of body; probably 12 or 13 

 types (15 or 16 if accessory organs are 

 counted separately). 



Lampadioteuthis In tentacles; subocular; intrapallial; prob- 

 ably 7 or 8 types. 



Abralia astrolineata, \ 



Abraliopsis, .Integumentary; tips of ventral arms; sub- 



Watasenia, ocular (dimorphic). 



Pterygiotenthis Tentacular; subocular; intrapallial; 8 types. , 



Pyroteuthis Tentacular; subocular; intrapallial; prob- 

 ably 8 or more types. 



18 Unequal in size, but showing clear structural evidence of homology. 



