The mating activities of the squid, Sepiella maindroni, were observed in the aq-uariums on Tsing-pan Island, Chou shan, Chekiang, under experimental conditions fromMay to June 1960 and May to July 1963 and 1964. Eyery year from April to June,the squids migrate to inshore areas for spawning. The mantle lengths of the male andfemale specimens under observation range from 7. 1 to 11.5 Cm. Copulation activities occur frequently. Postures of squids in copulation are shownin Fig. 1. From the observations we found that the male passes spermatophores tothe female's oral region. The sperm-mass is discharged and attached to the buccalmembrane and at the base of the left lateral arms of the female. The outer tuniclesof spermtophores are often formed in the female's stomach. The egg membrane is formed in the arms of the female. At first, the arms curvedown and the base of which rounds up to form a cavity into which her funnel extends,then nidamental glands and oviductal gland secrete gelatin into it to form the egg mem-brane, and finally, the egg passes through the funnel into the membrane. The black pig-ment of the egg membrane comes from its own ink sac when the egg membrane is beingformed. It seems that the fertilization of the squid's eggs takes place near the buccalmembrane.