Ernest Everett Just

How do fertilization envelopes form?

contributed by Aaron Slater


Animals, Aquatic, Cellular biology, Field, Fundamental research, Historical figure, Lab, Marine, North America, Observational, Organismal biology, Person of Color, Race/ethnicity, Societal Relevance


View and download in google slides here

Note: click the gear symbol or see below for notes that accompany the presentation

Other Resources

W. Malcolm Byrnes and William R. Eckberg. 2006. Ernest Everett Just (1883–1941)—An early ecological developmental biologist. Developmental Biology 296:1-11. link

Presentation Notes

Researcher’s Background

Ernest Everett Just was an early 20th century African American embryologist that had a profound interest in fertilization and egg development processes of marine invertebrates. 

Biography in brief

Just started his academic endeavors attending Dartmouth College, afterwards joining the faculty of Howard University. During his summers he worked at the Marine Biological Laboratory in Woods Hole, Massachusetts. There he was able to expand his knowledge by studying marine species in lab and in their aquatic habitats. He published many scientific articles and has been acknowledged in many research societies for his noteworthy experimental embryology studies propelling our understanding in marine biology.

Axes of identity & underrepresentation

It was harder to do good research in the states during his time because of institutionalized racism which set limits on his behalf. Just found more opportunity in Europe.

Research Overview

Take home message of study

Just studied various species to understand how marine invertebrates developed over time. While at Woods Hole research station he had the opportunity to explore parthenogenesis in eggs of marine animals. Parthenogenesis is the process of a female making a viable egg that grows into an adult without the fertilization from a male. 

Just focused his research on the events of egg cell transformations following initial sperm-egg interaction. These fertilization envelopes called vitelline envelopes is an extracellular fibrous layer on the outside of an embryo in non-mammalian species to help protect the egg through its development. The fertilization envelope changes over time allowing for a greater understanding of developmental biology. Two marine related species studied by Just was Echinarachnius parma (the common sand dollar) and Chaetopterus pergamentaceus (the parchment worm). 

Study system

Photographs of marine invertebrates Just studied. Source: Byrnes and Eckberg 2006
(A) Echinarachnius parma (sand dollar)
(B) Chaetopterus pergamentaceus (parchment worm)
(C) Platynereis dumerilii (nereid worm)
(D) Arbacia punctulata (sea urchin)
(E) Nereis limbata (clam worm)

Key Research Points

Key figure

The egg fertilization envelope of sand dollars. Just found that the fertilization envelope is mediated as a result of wave motion and environmental sources causing structural change for the ectoplasm (outer membrane).

Societal Relevance

Just’s contributions allowed him to disprove and correct many theories in the field of embryology. His persistence gave way to a higher importance on egg cell surface development studies, furthering research efforts into marine species development, inheritance, and evolution.

Leave a Reply

%d bloggers like this: