ANATOMY AND LIFE HISTORY OF MOLLUSCA. 131 



outside, perforating the choroid, and end at the surface of the shell, 

 or round the cornea, apparently forming a sensitive zone round 

 each eye. 



Mr. Mosely was not successful in finding these eyes in all the 

 genera of the family. They were entirely absent from the genus 

 Chiton and some others. In that genus the perforations and 

 sense-organs were present, but no eyes. In Chiton (Corephium) 

 aculeatus, L., the eyes were present in enormous numbers. He 

 reckoned there must be 8,500 eyes. This is an Australian 

 species. In Chiton (Tonicia) marmoratus, Grael, the eyes are sunk 

 in little pit-like depressions on the shell-surface. He searched in 

 vain also for any similar eyes in the shells of Patella., and other 

 allied genera. He regarded the shells of the Chitonidae as 

 possessing a feature peculiar of its kind, entirely unrepresented 

 in other Mollusca. 



It need hardly be said that so important and interesting a 

 discovery made quite a sensation amongst naturalists, and the 

 wonder was that such numerous organs should so long have 

 awaited discovery. So important was it deemed that at the 

 British Museum at South Kensington, in the portion devoted to 

 marine conchology, the Chitons were brought into prominence for 

 the benefit of visitors. One of the shells is conspicuously labelled 

 for exhibition, and an enlarged model is placed by the side, showing 

 the eyes on the surface of the shell, the prominent rounded 

 tubercles on the tegmentum beside them, and minute protuberances 

 for pores containing nerves of sense. 



Before dealing in detail with what instances Australia 

 furnishes of this remarkable character, a few preliminary remarks 

 must be made. One of the shells on which Prof. Mosely made 

 his most important observations was an Australian Chiton, that 

 is Chiton (Corephium) aculeatus, which is very common in 

 Sydney Harbour. It is probable that the other genera amongst 

 which he searched in vain for shell-eyes were European species, 

 and possibly the shells were not preserved in spirit, in which case 

 the eyes would be difficult to discover. One further observation 

 has to be made. 



It has already been remarked that these shells are nacreous. 

 In the case of Patella tramoserica, Martyn, which is the species with 

 which we have been dealing previously, it will be remarked when 

 looking at the shell from the inside that there is a narrow margin 

 at the extreme edge, passing all round the nacreous inner line. 

 This is where the outside plate or tegmentum overlaps the internal 

 or nacreous lining. A similar structure is seen on a very great 

 number of shells, whether they are nacreous or not, and I call 

 attention to it here as an illustration of the conspicuous way 

 in which the double-plated structure is universal amongst the 



