BIFURCATION IN THE EMBRYOS OF TUBIFEX

1. Tubifex tubifex (Müll.) deposits from one to seventeen eggs per cocoon, a few of which are often sterile.

2. Emergence of young worms from the cocoon is exclusively through two oppositely located apertures.

3. Various forms of abnormality commonly appear among the developing worms, chief among which are bifurcations of the body. Approximately twenty percent of the cocoons examined contained bifurcate embryos. This is the first report of bifurcation as an embryonic phenomenon in any of the lower famiies of the Oligochæta.

4. Diverse forms of bifurcation involving both extremities of the body occur in either simple or compound form.

5. Of more than four thousand recently emerged worms examined only ten bifid individuals were found. Any departure from normal body form involving increase in diameter constitutes an extremely effective barrier to escape from the cocoon and practically all of the numerous abnormalities are automatically eliminated.

6. While bifid worms may live for long periods of time imprisoned within the cocoons, emergence is a rarity.

7. Attempts to rear bifid individuals have thus far been unsuccessful.

8. An examination of more than one thousand worms from natural habitats and representing various stages of maturity yielded no bifid forms.

9. A preliminary morphological study, based principally on the setæ, the nervous system, the nephridia, and the circulatory system, shows the body region of these monsters to be double in composition while the bifurcate portions simulate the normal tubificid structure.