Figure 2
From: Posterior regeneration in Isodiametra pulchra (Acoela, Acoelomorpha)
Sagittal sections through copulatory organs of a control specimen. Anterior is to the left in all panels. A. Electron micrograph of bursal nozzle. Note the sperm extending through the canal from the seminal bursa (right) into the vestibulum (left) and the numbers of cells that constitute the structure. B. Histological section through copulatory organs. Arrowheads point to female sphincter. Note that the connection of the vagina to the bursal stalk posterior to the sphincter is an exception and not the rule. Abbreviations: bn, bursal nozzle; bs, bursal stalk; ds, digestive syncytium; ep, epidermis; ma, male antrum; p, penis; pg, prostatoid gland cells; sb, seminal bursa; sv, seminal vesicle; v, vagina; ve, vestibulum. Scale bars: A 2 μm; B 50 μm.