254 A MONOGRAPH Or THE AUSTRALIAN APHRODITEA, 



existence of nerves in the elj'tra, and their occurrence seems to 

 have been first noticed by Ehleas.f In Pohjno'c pellucida the 

 latter found a nerve entering the scale through the scale- 

 tubercle and giving off radiating branches. A similar arrange- 

 ment is very well seen in the scales of Aphrodita and some 

 species of Lepidonotiis and Polynoe, and is specially conspicuous 

 after strong staining with haematoxylin or cochineal. The nerve 

 divides near the point of entrance into numerous branches 

 which radiate towards the periphery, and become divided again 

 and again, giving off numerous minute twigs. In Folyno'c 

 pellucida Ehlers has traced each twig to one of the hollow i)rocesses 

 on the surface of the scale. This definite termination of each 

 twig may be well seen in successfully stained elytra of other 

 species, and there can be little room for doubt that the papilla) 

 on the surface of the scale are, in most instances at least, end- 

 organs for the elytral nerve. 



The functions with which the scales may be supposed to be 

 connected are (1) protection, (2) the production of phosphorescent 

 light, (3) sensation, (4) respiration, and (5) incubation. 



The protective function of the scales is in some instances the 

 predominating one. Tiius in Iphione the scales are of extreme 

 density and cover the entire dorsal surface with an armour which 

 the animal is incapable of throwing off when irritated, and which 

 gives it a remarkable superficial resemblance to Chiton. In 

 others the scales, though tough, are more rearlily detached, 

 and in some cases they do not completely cover the dorsal surface ; 

 while in many species of Polynoli they are so delicate, and so 

 readily parted with on the slightest irritation that their direct 

 protective action must be very slight. The greatest reduction of 

 the protective function is, however, met with in Aphrodita and 

 some allied genera, in which the scales are covered with a thick 

 layer of matted hairs which form an efficient protective covering 

 to the dorsal surface. 



t L. c, p. 110. 



