BROOKS AND RITTENHOUSE: ON TURRITOPSIS. 
459 
8. The formation of the endoderm follows none of the typical 
methods described by Metschnikoff. It arises late in the larval life 
from the syncytial mass of tissue left in the interior of the embryo 
after the separation of the ectoderm by the mesogloea. When the 
cells first reappear they are crowded together without any definite 
arrangement; finally they come to form the distinct endodermal 
layer. 
9. During the late segmentation there is evidence that some of the 
nuclei divide amitotieallv. 
«/ 
10. The planula becomes attached on the side by nearly its entire 
length, and is transformed into a root. 
11. The first hydranth develops from a bud which is given off at 
about the middle of the root soon after attachment. 
12. The tentacles develop in indefinite whorls. Each whorl has 
four tentacles. The oldest are nearest the distal end. In the fully 
developed hydranth they have the appearance of being scattered 
rather than of being arranged in circles. 
LITERATURE. 
Brooks W. K. 
’83. Notes on the medusae of Beaufort, N. C. Studies from biol. lab. 
Johns Hopkins univ., vol. 2, p. 465-475. 
’84. On the life history of Eutima, and on radial and bilateral symmetry 
in hydroids. Zool. anz., vol. 7, p. 709-711. 
’86. The life history of the Hydromedusae. A discussion of the origin 
of the Medusae and the significance of metagenesis. Mem. Boston 
soc. nat. hist., vol. 3, p. 359-430, pi. 37-44. 
Bunting, M. 
’94. The origin of the sex-cells in the Hydractinia and Podocoryne; 
and the development of Hydractinia. Journ. morph., vol. 9, p. 203- 
236, pi. 1-3. 
Gerd, W. 
’92. Zur frage liber die keimblatterbildung bei den hydromedusen. 
Zool. anz., vol. 15, p. 312-316, pi. 28, 5 figs. 
Hargitt, C. W. 
’00. A contribution to the natural history and development of Pennaria 
tiareUa McCr. Amer. nat., vol. 34, p. 387-415, 4 pis., 2 figs. 
’04a. The early development of Pennaria tiarella McCr. Arch, f. entwick- 
lungsmech. d. organ., vol. 18, p. 453-488, pi. 24-28. 
