146 
Of Brissopsis lyrifera ripe specimens were found already in 
the middle of August in 1918, though only few females, the great 
majority of the females being still unripe. In the summer of 1919 I 
did not succeed in finding a single ripe female before the 3rd of Sept¬ 
ember, while ripe males were found already on the lst of August; 
in the later part of August the males, upon the whole, were so full 
of ripe sperm that one could not help wondering how they could 
wait the rather long time till the females would become ripe. — I 
may mention here that on a dredging trip the first of September 1919 
to the inner part of the Gullmar Fjord I observed a number of 
unusually large specimens of Brissopsis in which the genital organs 
were quite black, without the slightest indication of sexual products. 
I have no doubt that these large specimens were really quite senile 
and had passed the age of sexual reproduction; the matter would 
be worth while a doser investigation. 
In the summer of 1918 artificial fertilization of Brissopsis was 
tried several times, but without success. Again in 1919 I repeated 
the experiment, but always without succes. The fertilization mem- 
brane was formed, but there was no cleavage. Evidently this spec¬ 
ies is exceedingly sensible, in marked contrast to other Echinoids. 
It may be suggested that it was the somewhat higher temperature 
in the laboratory which was unfavorable to the development of the 
eggs. But this can only be ascertained by renewed experiments. 
Since it was thus found impossible to rear the larva from the 
egg under usual laboratory conditions, there was only the hope of 
finding it in the plankton. The larvæ of Echinoccirdium cordatum 
and Spatangus purpureus being known, that of Echinocardium 
flavescens being eliminated on account of the much earlier breed- 
ing season it might be stated with certainty that, if a new Spatan- 
goid larva turned up in the plankton about the middle of Sept¬ 
ember, it could be nothing else than that of Brissopsis lyrifera. 
This was exactly what happened. By this time a young Spatangoid 
larva different from that of Ech. cordatum (the .larva of Spatan¬ 
gus purpureus was never met with at Kristineberg) appeared in 
considerable numbers, and soon more advanced specimens were 
found; larvæ in beginning metamorphosis were found already about 
the middle of September in 1918 (— in 1919 they were not found 
in so advanced stages by that time in accordance with the faet 
