Slide showing diagram illustrating the 'Structure of Trochosphere of Eupomatus.' Slide shows diagram illustrating the 'Structure of Trochosphere of Eupomatus.' Diagram is labelled with letters 'M', 'A','S','N','S.O.', 'E', 'ME', 'AV'. The corresponding key reads as follows: 'Fig. 142. - Diagram showing structure of Trochosphere of Eupomatus. - After Shearer. M., Mouth; A., anus; S., stomach; N., larval kidney; S.O., apical sense organ; E., eye-spot; M E., beginning of mesoderm; A.V., anal vessicle.' Late 19th to early 20th century