744 Proceedings of Royal Society of Edinburgh. [sess. 
During 1902 (Table II.) only two species were found to be 
abundant or very abundant ; namely, — 
Margellium odopundatum, on May 5th and 12th. 
Hybocodon prolifer, on May 5th. 
For comparison I must select Yalencia harbour, as it is the only 
place I know of wdiere continuous records on medusae have been 
kept for a whole year. 
In 1897, the following species of Hydromedusse were found in 
shoals or in great abundance : — 
Corymorpha nutans , May and June. 
Sarsia prolifer a, July. 
Dipleurosoma typicum , July and August. 
Euchilota pilosella, June. 
Obelia nigra, July and August. 
Phialidium cymbaloideum , March, May, June and July. 
Phialidium temporarium, May, September and October. 
Solmaris corona, July and September. 
In 1898, all the above species, except Sarsia prolifera, again 
occurred in vast quantities, and Laodice calcarata occurred in 
shoals in July and August. 
I can only account for the scarceness of the Hydromedusse by 
the scarcity of hydroids. Although the hydroids found in the 
Clyde make up a long list of species, yet I noticed (on my two 
visits), when out trawling in the “Mermaid,” and when looking at 
the material which was brought into the Laboratory, that hydroids 
were usually scarce. 
The Seasonal Changes in the Medusqid Fauna. 
As a rule in our seas during the winter months — December, 
January and February — medusse are very scarce. They begin to 
make their appearance about the middle of March. The time of 
their first appearance depends mainly upon the temperature of 
the sea, so that in one year they may be earlier than in another 
year. 
Certain species (belonging to Obelia and Phialidium), which 
occur early in the spring, will be found throughout the summer 
