In the ventral cord no small fibrils were seen only rather small fibers which may have been fibrils. The lack of connective material in part at least, perhaps because the nervous system is often extended and folded, shows the cell processes with great distinctness. This may be why a clearer picture than usual is presented of the relationship of cells. Cells are abundant on the ventral side of the cord, especially in the middle line. The more dorsal fibrous region is practically without cells of any kind. No very marked tracts of fibers are evident, the fibers are about equally distributed in all directions and may be subdivided as follows: 1. Fibers which enter the fibrous mass from cells and run short distances up and down. 2. Fibers which pass from cells to other cells near by in the cellular area. 3. Fibers which leave the ganglion laterally from ventral cells. 4. Fibers which enter from the lateral nerves to end in the fiber area or in among the cells. There are no indications of long fibers, either ascending or descending. After the examination of the cord of this animal one is impressed with the suggestion that many cells of similar sort act alike, that is groups of cells, not individuals are involved in the simplest transmissions of impulses. This general suggestion which, of course, is not new, comes to mind with great clearness after the study of thin sections of the cord of this animal. Whether the cells actually anastomose or not is a question hard to decide, but in the numerous contacts of naked fibers there is, I believe, ample opportunity for the transmission of complex changes from cell to cell, to all parts of the nervous system. In this form there is no particular localization of definite centers. The brain differs in structure from the cord, the central fibrous mass is more dense, the cells are very much smaller and more numerous. Some cells of the brain send their fibers out directly without the common pathway of a distinct nerve trunk. No special features of the brain were determined except the cerebral organs already described. _Andreae_ 1882 Beitrag zur Anatomie und Histologie des Sipunculus nudus. Zeit. f. Wiss. Zool. t. xxxvi. _Andrews, E. A._ 1887 Notes on the anatomy of Sipunculus gouldii Pourt. Studies Biol. Lab. J. H. univ. vol. iv. _Delage et Herouard_ 1897 Traite de zoologique concrete. Les vermidiens. vol. v. Paris. _Haller, B._ 1889 Beitrage zur Kenntniss der Textur des Central nervensystem Hoherer Wurmer. Arb. des Zoolog. Inst. Wien Tom. viii. Heft 2. _Marcel, A. Herubel_ 1907 Recherches sur Sipunculides. Chap. iv. Le system nerveux. Mem. soc. d. France. t. xx.