Actiiiiae. 309 



Plate LII. 



Brood Ohamhers and EmhryoR. 



Fig. IG. — Longitudinal section through larva of U. sulcata taken from brood 

 chamber. 



Fig. 17. — Transverse section of the same, showing developing mesenteries. 



Fig. 18. — Specimen of U. carlgreni killed with brood chamber open and with an 

 embryo escaping. 



Fig. 19. — The same with incision through outer wall of chamber and body-wall. 



Fig. 20. — Transverse section through advanced embryo of U. sulcata showing 

 about one-sixth of the section. 



Fig. 21. — Transverse section tlu-ough the sphincter muscle of the same. 



