CASSIOPEA XAMACHANA. 235 



PLATE 33. 



Fig. 2fi. Strobila, in which the degeneration of the rhopalial tentacles is nearly completed, and the inteirhopalial 

 tentacles have begun to degenerate. 



Fig. 20. A complete slrobila. The basal polyp bears a bud which broke off and swam away while the drawing was 

 being made. The ephyrula was detached during the following night. The rhopalia are visible through the umbrella. 

 At y, is a pair of twin rhopalia ; compare i/, Fig. 30. 



Fig. 27. The basal polyp of the same specimen, a few hours after the separation of the ephyrula. 



Fig. 28. Optical section of the same. 



Fig. 29. An ephyrula recently set free. Oral aspect. The gastric filaments are visible through the mouth. X 31. 



Fig. 30. A specimen of about the same age, showing variations of the margin at u, w, x, y and z. X 31. 



PLATE 34. 



Fig. 31. Mouth parts of a young medusa in the Aurosa stage. The gastric filaments may be seen through the central 

 mouth opening. X 33. 



Fig. 32. Oral disc of an older specimen. The oesophageal tubes appear as light areas, one at the junction of each pair 

 of labial grooves. 



Fig. 33. One of the oral arms from the same specimen as Fig. 32. 



Fig. 34. Floor of the stomach ami the oral arms of an adult viewed from the aboral side. The roof of one subgenital 

 cavity is removed, and a thread is represented as passing through the external orifice into this cavity, at f.. The ultimate 

 branches are represented on only one of the oral arms. 



Fig. 35. Portion of the aboral surface of an adult. About half natural size. 



PLATE 35. 



Fig. 36. Section of a young bud. X Zeiss DD -|- oc. 2.' 



Fig. 37. Diagram to show the branching of the septal muscles, SHI,, SIM.,, sm 3 and si 4 , and the connections of the 

 septal muscles of the bud, SHI',, sin'.,, and sm' 3 . Reconstructed from the series of sections of which Fig. 30 is one. 



Fig. 38. Section through the distal apex of an older bud, showing the attachment of a septal muscle to the ectodermal 

 epithelium. X Zeiss H -f- oc. 2. 



Fig. .'!!>. Longitudinal section of a planula-like larva. 1> was the distal, and P the proximal, end of the bud while 

 attached. X Zeiss DD + oc. 2, dt. 100. 



Fig. 40. Longitudinal section through the posterior end of a swimming larva, in which changes preparatory to the 

 formation of the mouth are taking place. X B & L i -f- Zeiss oc. 2. 



Fig. 41. Similar section of a slightly older larva, showing the mouth as a small opening not exceeding in width the 

 thickness of the section. X B & L J + Zeiss oc. 2, dt. 160. 



Fig. 42. Adradial section of a scyphistoma a little older than Fig. 9 (5th day). X Zeiss DD + oc. 2. 



Fig. 43. Obliquely transverse section of a specimen of the same age, showing the greatest width of one septum, x B 

 & L J + Zeiss oc. 2, dt. 160. 



Fig. 44. A tangential section of an older larva, showing the connection of a septal muscle with the circum-oral disc. 

 X Zeiss H-f oc. 2. 



PLATE 36. 



Figs. 45 to 47 are consecutive transverse sections of one individual. Fig. 45 shows the continuity between the endoderm 

 of adjacent gastric pouches at the base of an interradial tentacle. Fig. 47 is lower, and here the gelatinous septum com- 

 pletely separates the two pouches. X Zeiss H -f- oc. 2. 



1 Unless otherwise noted, the microscope was used with the tlraw tube not drawn out. Length of tube (dt.) = 137 mm. 



