44 LIVING LIGHTS. 



Some of the most remarkable moUusks are found among 

 the sea-slugs, so called from their resemblance to the slugs 

 of the garden. I have found them on the weed floating in 

 the Gulf Stream, so resembling the latter in almost every par- 

 ticular that it was difficult to determine that they were not 

 a part of the weed itself. Scyllaea pelagica is such a form ; 

 helpless, yet finding protection in its mimicry of the sur- 

 roundings. Equally as remarkable is Dendronotus,^ the 

 bushy sea-slug whose gills resemble the branches of weed in 

 a remarkable manner. This curious sea creature is quite 

 common on the seaweeds of our New-England beaches. 

 In the Mediterranean and Pacific is found the most unique 

 of the group, the Phyllirhoe hucephala (Plate V., Fig. 2), 

 which differs from many so entirely that it would seem to 

 belong elsewhere. Like the other forms, it is pelagic, often 

 being seen swimming along, resembling a fish, with its com- 

 pressed body, and vertical, fan-like tail, and with long feelers 

 or tentacles ahead. It is transparent and shelless in the 

 adult stage, possesses no foot or branchice, evidently breath- 

 ing through the body-walls or general surface. To add to 

 its curious features, the Phyllirhoe is brilliantlj^ phosphores- 

 cent; light being emitted from certain spots, shown in the 

 Engraving, rendering the tissues transparent and luminous. 

 Examination has shown that the liglit proceeds from certain 

 globular nucleated cells, which appear to be the terminations 

 of nerves. 



The Phyllirhoe thrives well in the aquarium, and has been 

 studied and observed in the famous aquarium at Naples. 

 When it is touched or is swimming, the light seems to diffuse 

 the entire surface, so that it presents a striking contrast 

 against the dark water ; and undoubtedly this gift is a fatal 



