790 
Proceedings of Royal Society of Edinburgh. [sess. 
Oikopleura dioica (Fol). 
? Oikopleura flabellum r J. Muller. 
Oikopleura d,ioica , Lohmann, 1901, iii. p. 17, fig. 20. 
In 1901, during April it was fairly common, but became scarce 
in May. On 3rd June a shoal suddenly appeared. The shoal 
quickly decreased in number, and after the middle of June 
Oikopleura again became very scarce. During July it was fairly 
common. Records were not kept for the remaining months of the 
year. 
In 1902, it was taken in every month throughout the year.. 
During January, February, and March Oikopleura was always very 
scarce, and specimens were only occasionally taken. On 3rd April 
it suddenly became common, and was very abundant on 23rd 
April. It was common during May, but was decreasing in 
numbers towards the end of the month, and was very scarce 
throughout June. During June and July both young stages and 
small adults were taken. About the middle of July Oikopleura 
became common, and remained fairly common till early in August, 
when it began to decrease in numbers. On 25th August it again 
suddenly became abundant, and during the first week in September 
there was a dense shoal of large adults. They rapidly disappeared 
about the middle of the month, but there was an increase in 
numbers again towards the end of the month and in the early part 
of October. 
On 8th October there was another sudden increase in numbers, 
and large adults with gonads became very abundant. This shoal 
remained for about a week, and then quickly disappeared. 
Oikopleura was very scarce at the end of October. 
During the second week in November Oikopleura became 
common, when large adults with gonads were taken ; but again 
they soon disappeared, and there was a great scarcity towards the 
end of the month. 
Throughout December a few specimens, young stages and adults 
with gonads, were usually present in the nets. 
The most remarkable character about Oikopleura was the 
