ON THE MARINE BIOLOGICAL LABORATORY, PLYMOUTH, 439 
In order to obtain good results it is first of all necessary to use none 
but fully developed and thoroughly ripe males and females for the experi- 
ment. It is possible to get ripe eggs and spermatozoa from under-sized 
individuals, and also from ovaries and testes, the greater bulk of which con- 
sists of unripe sexual] cells ; but in no case did the larve produced from 
these live more than a short time. When the genital organ is ready at a 
touch to dissolve into eggs or spermatozoa, then and then only may 
success be anticipated. 
The great essential condition for success is that the larve should be 
placed in pure sea-water, brought from some distance from the shore. In 
Plymouth the water must be brought from beyond the breakwater. And 
hence the success of any experimental work at Plymouth depends entirely 
on the possibility of procuring a continuous and abundant supply of this 
‘outside’ water. Lest it should be thought that this is only necessary in 
the case of Echini, I may mention the fact that although Asterina gibbosa 
will live in the tanks and lay its eggs there, these invariably fail to 
develop. Nevertheless, in Naples every year crowds of the larve of this 
hardy species are obtained by simply throwing the adults into the tanks 
and leaving them there under the ordinary circulation. 
Mr, Allen, the courteous director of the Plymouth Laboratory, strained 
the resources at his command in order to provide me with an abundant 
supply of pure water ; but the only method of bringing it to the Labora- 
tory at present available is carriage on the backs of the servants of the 
Laboratory from theshore to a height of over 100 feet, and it is obvious 
that under these conditions the amount available is very limited. One 
cannot help feeling that if Plymouth is to become successful as a centre 
of scientific work some capital expenditure must be incurred in order to 
provide for the better transport of ‘outside’ water to the Laboratory. 
As soon as the eggs had reached the blastula stage and had become 
free-swimming, they were decanted off from the remainder which had 
developed abnormally or not at all. The blastule were then transferred 
toa number of two-gallon jars, each fitted with the plunger devised by Mr. 
Browne, of University College, London. 
It is absolutely necessary that the jars should be protected from direct 
sunlight ; for this purpose a sheet of blackened paper was attached to the 
exposed side. 
If the action of the plunger be stopped, the larve, if healthy, will in 
a short time reach the top ; it is then possible to siphon off the bottom 
water. 
This, however, was not often done, and on one occasion some larvie of 
Echinus miliaris lived for a month in one of these jars without progressing 
beyond the stage usually reached in seven days. The tendency of these 
larvee to, so to speak, ‘hang’ in development without progressing, renders 
it impossible to make accurate statements as to the time they normally 
require to metamorphose. Even under the best conditions obtainable in 
a laboratory, it is probable that development is slower than in the open sea. 
At the end of about a week it was usually found that in one jar (ten 
in all were used) the larvee were particularly healthy and advanced. All 
the others were then discarded, and the healthy larvz distributed over the 
remaining jars, which were, of course, filled up with fresh sea-water. After 
another week the most healthy were transferred to ten-gallon jars fitted 
with large plungers. About 200 were put in each jar, and they then 
commenced to develop the spines and tube feet of the adult Echinus. 
