-236 ROBERT PAYNE BIGELOW ON CASSIOPEA XAMACHANA. 



Figs. 48 and 49 are from the same series. Fig. 48 is the second section below Fig. 47. It just clears the oesophagus. 

 Fig. 49 is through the upper part of the stem. X Zeiss DD -f oc. 2. 



Fig. 50. Longitudinal section of a scyphistoma with sixteen tentacles, probably a little younger than Fig. 15. X Zeiss. 

 DD + oc. 2, dt. 195. 



Fig. 61. An obliquely transverse section of a fully developed scyphistoma, showing the relations of the septal muscles 

 to the depressions in the circumoral disc. The mesogloea is shaded. X Zeiss B + oc. 2, dt. ICO. 



Fig. 52. Part of an interradial section from a scyphistoma a little older than the last. Owing to a slight obliquity of 

 the section, the full extent of the circular sinus at the base of the tentacle is not shown. It extends to the point marked x. 

 X Zeiss C + oc. 2. 



PLATE 37. 



Figs. 63 to 56 illustrate the development of the rhopalia. 



Fig. 53. Median section of the interradial tentacle shown in Fig. 52 ; x marks a corresponding point in the two sections 

 X Zeiss H + oc. 2. 



Fig. 54. A radial section from the base of a rhopalial tentacle somewhat older than Fig. 23. X Zeiss H + oc. 2. 



Fig. 55. Radial section of a rhopalium in the stage of Fig. 25. x Zeiss H -}- oc. 2. 



Fig. 56. Radial section of a rhopalium in about the stage of Fig. 26. X Zeiss H + oc. 2. 



Fig. 57. Radial section showing the course of a septal muscle in a strobila, at the stage of Fig. 24. X ZeLss DD + oc. 2. 



Fig. 58. A similar section from a specimen a little older than Fig. 25 ; x, point of separation between the two discs. 

 X Zeiss DD + oc. 2. 



PLATE 38. 



Fig. 69. Median vertical section of a strobila in the stage of Fig. 26 ; x, boundary between ephyrula and basal polyp. 

 X Zeiss B + oc. 2. 



Fig. 60. Portion of section from the same specimen, showing the proboscis of the basal polyp ; x marks same point as 

 in preceding. X B & L | + Zeiss oc. 2, dt. 160. t 



Fig. 61. Median vertical section of a basal polyp, stage of Fig. 27. X Zeiss B -f- oc. 2. 



Fig. 62. Part of a section from the same specimen, showing the proboscis, p, and the vestige of the former connection 

 with the ephyrula at x. X B & L + Zeiss oc. 2, dt. 160. 



Fig. 63. Median vertical section of an ephyrula that has recently become free ; x is opposite the opening that formerly 

 led into the cavity of the basal polyp. Cf. Fig. 29. x Zeiss DD -f oc. 2. 



Fig. 64. Median vertical section from a young medusa intermediate in age between Figs. 31 and 32. The section is 

 nearly interradial in position, x Zeiss AA + oc. 2, dt. 160. 



Figs. 65 and 66. Tangential sections of the same specimen, parallel to the last, nearly at right angles to an interradius. 

 Fig. 66 is the one nearer the periphery, x Zeiss AA + oc. 2, dt. 160. 



Printed, August, 1900. 



