"'Nurse' of Doliolum mulleri. I., Inhalant, E., exhalant aperture; C., ciliated band round pharynx (P.);…
"Sexual individual of Doliolum mulleri. G., gonads; B., gill-slits; I., Inhalant, E., exhalant aperture;…
"The colonies of these singular creatues are in the form of a cartilaginous tube, open at one end. In…