Much uncertainty would seem to exist in regard to two very extraordinary marine species of Copepoda. In one, _Calocalanus pavo_ the male possesses enormous antennæ, and a remarkable development of iridescent feather-like structures at the end of the body, arranged in a sort of open fan-work; the female has what may be called “normal” antennæ, and a brush-like tuft at the end of the body. In the other species—_Calocalanus plumulosus_—of which the female only is known, there is a similar arrangement of plume-like structures at the end of the body, but all but one are extremely small; the single plume differs from the rest in being of enormous length. Commonly these structures are regarded as mechanisms to reduce the expenditure of energy necessary to keep at the surface of the water, for these creatures inhabit the surface-waters of the open ocean. Many larval Crustacea inhabiting similar areas are in like manner kept afloat, or at any rate aided in keeping afloat, by the excessive development of spines. But if this be the purpose of these strange excrescences of _Calocalanus_ it seems curious that the female of C. pavo should not be similarly provided. If they are to be regarded as secondary sexual characters it is curious that the females of _C. pavo_ and _C. plumulosus_ should be so utterly dissimilar. The male of _C. plumulosus_ is unknown. On the whole, it seems more reasonable to regard these strange structures as mechanical aids to swimming rather than as secondary sexual characters. CHAPTER XIII SOME STRANGE MARRIAGE-CUSTOMS: AND VIRGIN BIRTHS The Courtship of the Cuttle-fish—The Sumptuous Cradle of the Argonaut—The Love-darts of the Snail—Hermaphrodites and the Dangers of Self-fertilization—Oysters and Beauty—Sex reduced to its Lowest Terms—Parthenogenesis and Virgin Birth—The Story of the Hive-bee—The Departure of the Queen—The New Queen and her Marriage-flight—The Celebration of the Nuptials and its Surprising Sequel—The Widowed Queen turns Executioner—The Queen as Mother—The Queen’s Daughters—Nursemaids’ Duties—Change of Work—The Drones and their Career—Food and Sex—The Bumble-bee and its Life-story.