Adaptations of Fishes 195 



dition. All of these, however, are greater or less modifications 

 of one type. This type includes, according to von Lendenf eld's 

 views, three essential parts, i.e., a gland, phosphorescent cells, 

 and a local ganglion. These parts may have added a reflector, 

 a pigment layer, or both ; and all these may be simple or com- 

 pounded in various ways, giving rise to the twelve classes. 

 Blood-vessels and nerves are distributed to the glandular por- 

 tion. Of the twelve classes direct ocular proof is given for 

 one, i.e., ocellar organs of Myctophum which were observed by 

 Willemoes-Suhm at night to shine ' like a star in the net.' Von 

 Lendenf eld says that the gland produces a secretion, and he 

 supposes the light or phosphorescence to be produced either 

 by the ' burning or consuming ' of this secretion by the phos- 

 phorescent cells, or else by some substance produced by the 

 phosphorescent cells. Furthermore, he says that the phos- 

 phorescent cells act at the 'will of the fish' and are excited 

 to action by the local ganglion. 



" Some of these statements and conclusions seem insufficiently 

 grounded, as, for example, the supposed action of the phos- 

 phorescent cells, and especially the control of the ganglion 

 over them. In the first place, the relation between the ganglion 

 and the central nervous system in the forms described by von 

 Lendenf eld is very obscure, and the structure described as a 

 ganglion, to judge from the figures and the text descriptions, 

 may be wrongly identified. At least it is scarcely safe to 

 ascribe ganglionic function to a group of adult cells so poorly 

 preserved that only nuclei are to be distinguished. In the 

 second place, no structural character is shown to belong to the 

 ' phosphorescent cells ' by which they may take part in the 

 process ascribed to them.* 



' ' The action of the organs described by him may be explained 

 on other grounds, and entirely independent of the so-called 

 'ganglion cells' and of the 'phosphorescent cells.' 



* The cells which von Lendenfeld designates ' phosphorescent cells ' have 

 as their peculiar characteristic a large, oval, highly refracting body imbedded in 

 the protoplasm of the larger end of the clavate cells. These cells have nothing 

 in common with the structure of the cells of the firefly known to be phos- 

 phorescent in nature. In fact the true phosphorescent cells are more probably 

 the ' gland-cells ' found in ten of the twelve classes of organs which he 

 describes. 



