PAKIETAL SENSE-ORGANS OF GEOTRIA. 



On the Parietal Sense-organs and Associated 

 Structures in the New Zealand Lamprey 

 (Geotria australis). 



By 



Aitliur DciKly, D.Sc, F.L.S., F.Z.S., 



Professoi- of Zoology in King's College (University of Londou). 



With Plates 1 and 2. 



(a) Introductoky Remarks. 



Some years ago, whilst residing in New Zealand, I liad the 

 good fortune to obtain a plentiful supply of living specimens 

 of the New Zealand freshwater Lamprey, Geotria australis. 

 These specimens were all in what is known as the "Velasia" 

 stage of their development, none of them being sexually 

 mature, and all of them without the characteristic gular pouch 

 of the adult,^ They were, however, of considerable size, 

 averaging nearly a couple of feet in length, and the organs 

 which form the subject of the present memoir were probably 

 already fully developed. For the purposes of this investiga- 

 tion a considerable number of specimens were hardened and 

 preserved in a perfectly fresh condition by means of various 

 re-agents, of which absolute alcohol, Zenker's fluid, and 

 Flemming's solution yielded the most satisfactory results. In 

 some cases the head was simply cut oif and hardened in to to, 

 while in others it was partially dissected in the fresh state 

 before being placed in the hardening re-agent. 



Eight series of sections, longitudinal and transverse, were 



^ Por further particulars as to these specimens and the species to which 

 they belong vide Dendy and Olliver (1). 



VOL. 51, PART 1. NEW SERIES. 1 



