Name a group of invertebrate animals that is usually hermaphroditic

Many of the parasitic invertebrates like worms are hermaphroditic.

Explanation:

A hermaphroditic organism can be described as an organism that has bole male and female gametes and can produce both female and male reproductive organs. In animals like snails and worms, hermaphroditism allows either partner to become male or female. While many of the other organism can undergo self-reproduction.

Hermaphroditism can also be seen in plants mainly the angiosperms.

In humans, the people possessing this quality are called intersex humans.

your answer is "the 1950's"