The early stages of the two species of Pinnotheres occurring at Plymouth have been reared in the laboratory from egg to megalopa for the first time.
P. pisum has four zoeal stages and a megalopa. The megalopal stage was reached in eleven weeks from spawning and six from hatching. These times are probably considerably longer than under natural conditions. The number of swimming setae of the zoeal stages is discussed.
P. pinnotheres has two zoeal stages and a megalopa. The megalopal stage was reached in about nine weeks from early egg and three weeks from hatching. The work on P. pinnotheres confirms that of Lebour (1928 a, b), who obtained the two zoeal stages from the plankton and reared the megalopa from these.
Some observations are given on habits and moulting of the zoeae.