gß e. 0. Whitraan 



Fig. 41. Different forms of germ-cells fouud in a transitional. Some are under- 



going divisioü. Acetic acid. 

 Fig. 42. Three nuclei and two germ-cells found in a secondary Nematogen, which 



contained nine free nuclei. Acetic acid. 

 Fig. 43. Four nuclei and three germ-cells, found in a secondary Nematogen, 



which contained five nuclei. Acetic acid. 



Piate 4. 



Figs. 44 — 47 Dicyemennea Eledones ; figs. 48 — 50 Dicyemcnnea gracile; figs. 

 51 — 59 Dicyema truncatum. 



All the figs. magnified 465/1. 

 Fig. 44. Dorsal view of a Khombogen. Farapolars [pp) short, alternating with 



the two proximate ectodermal cells. Osmic acid. Takeu from E. Aldro- 



vandi. 

 Fig. 45. The cephalic end of a living specimen (3.25mm long). The head is 



.275 mm long and .225 mm wide. The parapolar coUar broadest at its 



junction with the calotte. From E. moschata. 

 Fig. 46. Front view of the calotte, showing four ventral and five dorsal cells. 



Acetic acid. From E. moscJiata. 

 Fig. 47. Unliberated embryo (.2 mm long) from E. moschata. The 23 ectodermal 



cells seen in situ. Seen from oue side. Cells of the body in alternating 



pairs. Osmic acid. 



Dicyemennea gracile. 

 Fig. 48. From a young individuai mounted in baisam (.6mm long). Shows the 



central nucleus and eight germ-cells. 

 Fig. 49. Dorsal view of a typical calotte. Parapolars not thickened at their 



junction with the calotte. Acetic acid. 

 Fig. 50. Optical section of the calotte of a Khombogen (3.2mm long). The 



parapolars taper backward instead of forward as in fig. 44. Width of the 



calotte .06 mm; average width of the body .05 mm. Thickness ofthe 



ectoderm .005 — .007 mm. 



Dicyema truncatum. 

 Fig. 51. Optical section of an embryo (.09 mm long) from Rossia macrosoma. The 



polar cells form a hollow hemispherical calotte of the same width as the 



body. Osmic acid. 

 Fig. 52. Caudal portion of an individuai (.28 mm long) from Sepia ofßcinalis. 



The two caudal cells are here much smaller than usuai. 

 Fig. 53. Asmall example (.2 mm) from S. ofßcinalis. There are only 12 cotodermal 



cells besides the calotte, in alternating pairs. The outlines ofthe polar 



cells were not clear. Osmic acid. 

 Fig. 54. A young individuai (.2 mm) from Rossia macrosoma, with 14 ectodermal 



cells besides the polar cells. Osmic acid. 

 Fig. 55. Another young individuai from S. ofßcinalis, showing large pyriform 



caudal cells. From a specimen mounted in baisam. 

 Fig. 56. An unusual form from S. ofßcinalis. Length .15 mm. Two large cells 



near the middle resemble the caudal cells. Mounted in baisam. 

 Fig. 57. An example (.25mm long) from S. ofßcinalis. Total number of ecto- 

 dermal cells 22. Endoderm contained only 3 germ-cells. No central 



nucleus could be seen. The calotte has a lateral inclination. Acetic acid. 



