515 



The Owens College Ammocoete was, to judge from the size of the 

 sections, considerably older than the New Zealand specimen, and this 

 possibly accounts for certain differences in the arrangement of the 

 parts under discussion. It appears also to have been treated with 

 osmic acid, while the staining was eftected by means of iron Braziliu. 

 The columnar epithelium of te ciliated grooves is perhaps not quite 



Fig. 



Fi?. 6. 



Fig. 5. Similar section through the region of the recessus sub-pinealis. 

 Fig. C. Similar section at about the level of the hinder margin of the posterior 



commissure. 



All the figures, exce])t fig. 2, were drawn with the aid of the camera lucida 

 under Zeiss objective A, with eyepiece No. 3. Fig. 2 was drawn with the aid of the 

 camera under Zeiss objective D, eyepiece No. 'A. 



Explanation of Lettering. — Ar. 2\, araclmoidal tissue; C. G., ciliated groove; 

 C'h. PL, choroid plexus; Com. P., posterior commissure; G.HR., right ganglion 

 habenulae; Inf., Infundibulum ; Iter, aquaeductus Sylvii or iter; 3f.b.l., left 

 Meynert's bundle; M.h.r., right Meynert's bundle; M. C., connective tissue brain 

 case (membranous cranium); P.S., recessus sub-])inealis or infra-pinealis; Tr., 

 trabeculae cranii ; V. 3, third ventricle. 



in such a good state of preservation histologically as in the New Zea- 

 land specimen, but evidently has much the same character. Beneath 

 the posterior commissure the grooves are widely separated d from one 

 another (fig. 1) instead of being in close contact. Anteriorly (fig. 5) 



34* 



