84 CO. Whitman 



A bell-shaped calotte of a Rhombogen (2.1raiu long), from the dorsal 



side. The metapolars form a flaring collar to the elongated propolars. 



Others of a similar shape were found at the same time. Acetie acid. 



Calotte of a Nematogen (3.95 mm long), from the ventral side. Contained 



several embryos and numerons germ-cells. Only two free nuclei were 



Seen. Acetie acid. 



Ventral view of the calotte of a Rhombogen (2 mm long). Two free nuclei 



in the cephalic end of the endoderm. Acetie acid. 



Dorsal view of a very oblique calotte of a Rhombogen (ca. 3.5 mm long). 



Acetie acid. 



Head of a Nematogen (2.7 mm long) from the side, showing an embryo 



[vc) partially liberated. Acetie acid. 



The calotte and parapolars of a primary Nematogen (1.9 mm long) from 



the ventral face. Contained one lai-ge nucleus, a few embryos, and many 



genn-cells. Acetie acid. 



Another Nematogen from the ventral face (length 1.5 mm). A central 



nucleus, germ-cells, and embryos. Acetie acid. 



A secondary Nematogen (.55 mm long) from the right side. The central 



nucleus and the parauucleus lodged in the head, and near them a granular 



body which represents the remains of a germogen. This individuai has 



passed a Rhombogenic condition represtnted by a single Infusorigen. 



Acetie acid. 



Fig. 14. A primary Nematogen from the left side (length 1.1 mm). Contained one 

 vermiform embryo, a considerable number of germ-cells from .005 to 

 .008 mm in diam., and a single nucleus. Shows the two verruciform 

 cells in the hind half of the body. Acetie acid. 



Fig. 15. A middle portion of a large Dicyemennea Eledones , in a transitional 

 phase, showing the central nucleus [ne), two paranuclei («'), numerons 

 vermific germ-cells, and two Infusorigons in their last stage. The largest 

 cells in the lufusorigens measure .016mm in diam., the size of infusorific 

 germ-cells. They have large nuclei (.01 — .012mm) while the vermific 

 cells have small nuclei (.004 — .005 mm). The nuclei of the smaller cells 

 in the Infusorigens agree in size with those of the smaller vermific germ- 

 cells. These small cells are probably derived from the larger ones with 

 large nuclei by di vision. Acetie acid. 



Piate 2. 



Figs. 16 — 21 Dicìjcma typus; figs. 22 — 29 Dicyema microcephalum. 

 Fig. 16 magnified 280/1 ; fig. 22, 120/1 ; the remaining figs. 465/1. 

 Fig. 16. A young Rhombogen (.6mm long) from the left side, showing all the 



ectodermal cells in situ. Parapolars followed by two dorsal and one 



ventral cell. Four granular verruciform cells. Osmic acid. 

 Fig. 17. A fully formed embryo (.25 mm long). Total number of ectodermal 25. 



Cells loosened by acetie acid. Contained a central nucleus and eight 



germ-cells. 

 Fig. 18. A portion of a Rhombogen as seen in a living condition. No distinct 



outlines of cells. Ectoderm shows minute round granules. 

 Fig. 19. Side view of a small Rhombogen (1mm long). Anterior polar cells a 



little larger than the posterior. Osmic acid. 



