Some male rotifers have a copulatory organ.
In male spiders the second pair of appendages (pedipalps) are each modified to form a complex structure for both holding sperm and serving as the copulatory organs.
The gonadal ducts of gastropod females often secrete a protective capsule around the fertilized eggs; in males, the terminal portion of the duct is sometimes contained in a copulatory organ.
A rather complex copulatory apparatus consists of an evertible (capable of turning outward) penis, or cirrus, in the male and a canal, or vagina, in the female.
Pheromones play a role in sexual attraction and copulatory behaviour, and they have been shown to influence the sexual development of many mammals as well as of insects such as termites and grasshoppers.
They are labeled "hemi" because two occur in each male, although only one is used during a single copulatory event.
Male tuatara have no paired copulatory organ; they have saclike structures from which the paired hemipenes of squamates were likely derived.
Since the male has no external copulatory organ, sperm are released through a median pore on the ninth sternite, or abdominal plate.
Copulatory organs have developed independently in several groups of vertebrates having internal fertilization.
In considering the development of reproductive organs, distinctions must be made between: (1) the origin of sex cells (gametes), (2) the origin and differentiation of the sex glands, or gonads (ovaries and testes), and (3) the origin and development of the supporting parts of the reproductive system (e.g., genital ducts, copulatory organs).
The effects of gonadal hormones may be summarized as follows: Gonadal hormones induce growth of and maintain the cyclical function of the reproductive tracts, accessory sex glands, and copulatory or ovipository organs.
