46 
ANNIE MATTHEWS. 
These eggs were successfully reared in the Plymouth 
laboratory. The above data shows that A. digitatum 
spawns during two of the coldest and stormiest months of the 
year, when the supply of material is necessarily uncertain, 
and therefore the work of collecting the various segmentation 
stages is, as a rule, unavoidably spread over the whole of the 
spawning season. The colonies used for this paper came 
from the trawling ground between the Dodman and the 
E Idystone, i.e. outside and some miles west of Plymouth 
Sound. They reached the laboratory in good condition in 
buckets of sea-water, and after being well washed the ripest 
colonies were selected, the choice being easily made, as ripe 
ova are deep reddish-yellow in colour, and ripe sperm sacs a 
very opaque white. The colonies were then placed by them- 
selves in one of the laboratory tanks, through which a constant 
stream of sea-water circulated, care being taken to avoid 
overcrowding. As the colonies generally remain healthy for 
only a few days in the laboratory tanks, even under the most 
favourable conditions, rarely expanding fully and possibly 
never feeding, those chosen must be in the best condition and 
ready to spawn. 
Some hours later the circulation was stopped and the female 
colonies soon spaAvned in the still Avater. It seems essential 
to have the Avater still, as this is favourable to the necessary 
expansion of the very sensitive polyps. Simultaneously the 
male polyps discharged from their mouths large quantities of 
spermatozoa which SAvam freely and fertilised the floating 
OA r a. On microscopic examination the latter were then seen 
to be completely covered by a delicate fringe of spermatozoa 
Avliich gave them a pseudo-ciliate appearance, but the “ cilia,” 
i.e. the tails, of the spermatozoa were non-motile. 
It Avas impossible to distinguish the particular sperm which 
fertilised the ovum, or to say when this occurred. Different 
colonies began to extrude their ova at varying times of the 
day or night (unlike Renilla, which spawns only between 6 
and 7 a.m. ( 16 )). 
The eggs of any one colony were passed out con. 
