MARINE BIOLOGICAL STATION AT PORT ERIN. 101 



Copepoda is nearly 1,000 billion. Now a billion of Cope- 

 poda yields not less than 1,500 kilograms of dry organic 

 substance, and consequently in the 16 square miles of a 

 certain Baltic fishery the German biologists consider there 

 exists Copepod food for over 530 millions of Herring of an 

 average weight of 60 grammes. 



Two common Copepods are shown in fig. XII., 

 Temora longicornis at 9, and P seudocalanus elongatus at 

 12. Each of these is about J of an inch in length. The 

 late Mr. Isaac C. Thompson, E.L.S., was a well-known 

 authority on the Copepoda, and has written many reports 

 and papers published in our volumes. Mr. Andrew 

 Scott, A.L.S., is now our local worker on this important 

 group, and author of many of our reports. 



When a fine muslin or silk tow-net is drawn through 

 the water of Port Erin Bay for a few minutes, at almost 

 any time of the year, a number of small free-swimming 

 plants and animals are captured. Such organisms are 

 known collectively as " Plankton." Some of the more 

 minute and simple of these (Protozoa and Diatoms) were 

 shown in fig. I., while a number of the commoner and 

 larger kinds of " Plankton " are represented in fig. XII. 

 They are evidently a mixture of young and old belonging 

 to different groups of animals. 



1. is the " Nauplius," or larval stage of the lower 

 Crustacea, such as Copepoda. x 25. 



2. is Sagitta hipunctata, the arrow- worm, adult. 



x 2. 



3. is the larval stage of a univalve Mollusc. x 30. 



4. is an adult Tomopteris onisciformis, a curious 

 transparent worm, x 2. 



5. is the larva of a Polyzoon. x 30. 



6. is a larva of a Polychaete worm (Nerine). x 30. 



7. is the larva of a Star-fish, x 40. 



