2 AliTHUR DKNDY. 



cut by the paraffin uiethotl; some tlirougli the entire head, 

 and some through the brain, after removal from the cranium. 

 Most of the material was stained in bulk with Ehrlich's 

 liajmatoxj'lin, and some of the sections were counter-stained 

 on the slide by means of acid fuchsin or eosin. 



Sections of material fixed in absolute alcohol were found to 

 be particularly valuable for demonsti'ating the arrangement 

 of the pigment in the ''pineal eye," this pigment, as is well 

 known, being soluble in acids, and, therefore, often entirely 

 absent from material treated with strongly acid hardening 

 re-:igents, such as Flemming's solution or Zenker's fluid. 



I firit observed the very well-developed " piueal eye'' of 

 the New Zealand Lamprey in a Geotria Ammoccete which 

 had been preserved in chrom-osmic solution by my late col- 

 league Professor T. J. Pai'ker, and given to me for investigation 

 by his successor at the Otago University Museum, Professor 

 W. B. Benham. The present investigation, however, was 

 largely stimulated by the remarkable results obtained by 

 Studuicka in his researches on the minute histology of the 

 parietal sense-organs of the European Lampreys (Petro- 

 myzon), and I am glad to be able to a large extent to 

 confirm these results, and perhaps even to still further extend 

 our knowledge of these remarkable structures. My work 

 has been greatly facilitated by the recent publication of 

 Studnicka's admirable monograph on ''Die Parietalorgane" 

 in Oppel's ' Lehrbuch der Vergleichenden mikroskopischen 

 Anatomie der Wirbeltiere ' (2), which renders detailed dis- 

 cussion of the writings of earlier investigators superfluous. 



(b) TorOGRAPHICAL AnATOMY OP TUE FORE-BRAlN AND ITS 



Deeivatives. 



In its general characters the brain of Geotria in the 

 " Velasia" stage agrees closely with that of the adult Petro- 

 myzon. Externally perhaps the most striking difference 

 consists in the very distinct lobulation of the surface of the 

 large olfactory lobes (fig. 1, O.L.), while iuterually the division 



