Who described the algae Spirogyra in 1674 and named the motile organisms Animalcules, meaning ‘little animals’?

The correct option is Anton Van Leeuwenhoek.

Step-by-step Explanation:

1. Discovery and Description of Spirogyra (1674):
In 1674, the Dutch microscopist Anton van Leeuwenhoek observed pond water under his custom-built single-lens microscopes. He described seeing green, spiral-threaded filaments which are now recognized as the green algae Spirogyra.

2. Naming of Animalcules:
During his microscopic investigations of pond water, rainwater, and human saliva, Leeuwenhoek observed microscopic, single-celled organisms displaying active movement. He named these motile organisms "Animalcules", which literally translates to "little animals." Today, these organisms are classified as protozoa, bacteria, and other microscopic life forms.

3. Why the other options are incorrect:
- Maurice Wilkins: A 20th-century biophysicist who won the Nobel Prize in Physiology or Medicine in 1962 for his work on the structure of DNA.
- Robert Remak: A 19th-century embryologist and neurologist who made key discoveries in cell division, showing that new cells are generated by the division of existing cells.
- Barthelemy Dumortier: A 19th-century Belgian botanist who was one of the first to describe cell division in algae, but his work was conducted long after the 17th century.