THE DEVELOPMENT OF ALCYONTUM DIGITATUM. 
45 
(b) Corrosive acetic. 
(c) Bouin^s picro-formol-acetic. 
The above three reagents appeared equally good for 
preserving all stages, except when the structure of the 
spicules was required. Perhaps (c) was the best general 
preserving fluid. 
( d ) Osmic acid, for preparations showing spicules and 
nematocysts. 
(2) Staining reagents. 
(a) Delafield’s hematoxylin. For morulas, and well-stained 
segmentation spindles ; also for gland cells in the oesophagus 
and ventral mesenteric filaments. 
(b) EhrlicKs hematoxylin, as (a). 
(c) Borax-carmine and picro-nigrosin. For planulas and 
all subsequent stages ; for structure of mesogloea. 
(d) RanviePs picro-carmine, followed by Kernschwarz, 
after fixing with osmic acid. For spicule structure. The 
picro-carmine stains the nuclei, while the Kernschwarz 
stains the spicule and its surrounding protoplasm. 
(e) Iron-brazilin. Good for all settled stages, gland cells,, 
etc., in combination with some plasma stain, e. g. safranin. 
4. General Account. 
Ripe male and female colonies 1 of Alcyonium digi- 
tatum are brought in by the trawlers in the Plymouth 
district from early December to early February, and fertilised 
eggs were obtained : 
(1) Between January 27th and February 13th, 1912. 
(2) Between December 10th and February 10th, 191 2 — 
1913. 
(3) Between December 14th and February 10th, 1913— 
1914. 
1 Hermaphrodite colonies occasionally occur, male and female polyps 
being present. Hermaphrodite individuals are also sometimes found 
in these colonies, such exceptions finding a parallel in the case of 
Corallium nobile ( 11 ). 
