8 
GEOUGE E. NICI10L[-S. 
then hecoine impregnated. In Raia, in particular/it was 
noted that the cells of the “Daclikern” and of the suh-com- 
niissural organ were also unimpregnated, and, for that reason, 
were conspicuous as yellowish patches upon the almost black 
background. 
A modification of the method of Bielschovski, suggested by 
Stewart Patou (’07), was tried upon embryo Scy Ilium cani- 
cul a, and upon a small teleost (Esox) brain. In the case of both, 
successful impregnations were obtained, nerve-fibres being 
picked out in a deep blue-black, while unimpregnated tissue 
takes on a soft grey tint. Reissner’s fibre appeared homo- 
geneous, and showed no indication of the coloration to be 
observed in neuro-fibrillae, but took on the pale grey colour. 
The cells of the “ Dachkern ” and the giant cells of the cord 
became heavily impregnated, the network of neuro-fibrillae 
WMtliin some of these latter (in embryo Scyllium) being 
wonderfully defined. 
The material examined includes : 
Cyclostomi. — Pe t r om y zon f 1 u via ti 1 i s, I ch thy o m zo n 
(En t osp h e n u s) tridentatus (ammocoetes only), G«otria 
a u s t r a 1 i s, ]\I y X i n e g 1 u t i n o s a, B d e 1 1 o s t o m a c i r r h a t u m, 
B . ( P o 1 i s t o t r e m a) s t o u t i . 
Elasmobranchii. — Chimmra (Hydrolagus) colliei; 
Scyllium cauicula, Raia (three species), Rhina squa- 
t i n a . 
Ganoidei. — Lepidosteus os sens (larvae). 
'bELEOSTEi. — Some twenty or more species of the genera 
Esox, Anguilla, Phoxinus, Umbra, Gobius, Blen- 
nius. Gas ter os tens, Syn gnat bus, Agon us, Coftus, 
'I’rigla, Mugil, Rhombus, Gadus, Lab ru s, Loph i u s. 
Box, etc. 
Amphibia. — Both adults and larvai of Amblystoma sp., 
Salam.andra (two species), IMolge (two species), Rana (two 
species), and adults only of Uyla sp., Bufo vulgaris, and 
Bombinator igneus. 
Reptieia. — Two different sjiecies of Gecko, Lacerta 
