SEA-FISHERIES LABORATORY. 161 



2. Support for apparatus. 



3. Balanced beam. 



4. Tumbling box. At c a brass rod is rigidly fixed 



working freely in lignum vitse bearings fastened 

 to the frame. ab = 35J inches, ac = 27^ inches, 

 cd = 9^ inches, bb = 11 inches. Width = 12 inches. 



5. Wires to rods. 



6. End view of hatching tanks, containing little 



boxes for eggs. 



7. Waste pipes leading into main pipe, taking water 



to tumbling box. 

 a End view of top and bottom of main suspender. 

 b End view of suspenders of framework for wires and 



tumbling box. The suspender to the tumbling 



box works through a guide (</). 

 c Side view of tumbling box in its frame. 



Note on the Spawning of the Mussel (Mytilus edulis), 

 By A. Scott. 



The determination of the spawning period of the mussel 

 on the Lancashire coast has occupied our attention for 

 some time. Hitherto we have mainly examined the con- 

 dition of the reproductive organs, both in situ in the 

 living animal, and by thin sections of prepared material 

 during periods of twelve months. Tow-nettings from the 

 vicinity of the beds have also been examined for the 

 larvae. These investigations enabled us, approximately, 

 to state when the eggs were shed. It is obvious, however, 

 that all the information regarding the actual spawning, 

 the fertilisation of the, eggs, and the period that elapses 

 before the resulting embryos become free-swimming 

 larva* can only be ascertained by carefully observing the 

 living animal. It is not possible to do this under natural 

 l 



