MARINE BIOLOGICAL STATION AT PORT ERIN. 89 



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

 Crustacea, such as Copepoda. 



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



3. is the larval stage of a univalve Mollusc. 



4. is an adult Tomopteris onisciformis, a curious 

 transparent worm. 



5. is the larva of a Polyzoon. 



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



7. is the larva of a Star-fish. 



8. is " Pluteus," the larva of an Ophiuroid. 



9. is an adult Copepod, Temora longicornis. 



10. is Sarsia tubulosa, one of the Medusoids derived 

 from a Zoophyte. 



11. is Pleurobrachia pileus, an adult Ctenophore 

 related to Medusae. 



12. is P send ocal anus elongatus, an adult Copepod'; and 



13. is a pelagic fish-egg containing the young fish. 

 Coming now to rather higher and larger Crustacea, 



figure XIII. illustrates the Amphipods or Sand-hoppers, 

 and figure XIY. the Isopods or Sea-slaters. These two 

 groups are closely related. In the Amphipods the body is 

 compressed from side to side, the back is generally curved, 

 the legs are long, and face some forwards and the others 

 backwards (see fig. XIII., 1), while a favourite mode of 

 locomotion is by a series of leaps. The leap is effected by 

 means of the hindmost or tail legs, which are bent for- 

 ward under the body, and then suddenly straightened out 

 so as to toss the body up in the air. The Amphipod shown 

 at 1 (Orchestia littorea) performs this action. Some kinds 

 of these Amphipods are extremely common on our sandy 

 shores, especially under stones or pieces of decaying sea- 

 weed. Others, like the Corophium grossipes shown at 2, 

 burrow in the sea-bottom, where some construct tubes and 

 nests of mud or sea-weeds. The curious skeleton-like 



