180 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Reissner's Fibre in the Canalis centralis of Vertebrates.* — Mr. 

 P. E. Sargent finds a continuous rod or fibre lying within the lumen of 

 the canalis centralis, apparently the same as Reissner saw in the lam- 

 prey in 1860, aud apparently the same as an artifact described by various 

 authors. After making sure that it was not an artifact, Mr. Sargent 

 traced its course in various vertebrates, especially Teleosts. It ex- 

 tends through the whole length of the canalis centralis of the cord, 

 and continues cephalad through the fourth and third ventricles to the 

 anterior end of the optic lobes. Posteriorly the fibre can be traced 

 with little diminution in size until near the extreme end. Since 

 Sargent's paper was written, Studnicka has also described the fibre,! 

 which he regards (according to Sargent, mistakenly) as the result of 

 secretion by the walls of the neural tube. 



Nerve -terminations on Striped Muscles of Teleosts.} — Dr. F. 

 Supino has examined a large number of Teleosts, and finds that the 

 nerve-terminations on the muscle are not in the form of motor-plates, 

 but branch freely in the muscle. The terminations closely resemble 

 those which Retzius has described in Aslacus. In Teleostean fishes the 

 form of the termination is variable even in the same animal, and yet 

 more so among different species. 



Microcentrum in Smooth Muscle-cells.§ — Prof. M. v. Lenhossek 

 describes in detail, what K. W. Zimmermann has also observed, the 

 microcentrum in smooth muscle-cells (in the circular muscle-layer of 

 the cat's small intestine). The occurrence of the microcentrum in this 

 highly differentiated type of cell is of interest in corroborating the con- 

 clusion that the microcentrum is a typical component of the cell. The 

 author suggests that it may act in the smooth muscle-cell as a kino- 

 centrum, as it is supposed to do in some other cases. 



Importance of Nucleoli. (| — Herr Rohde emphasises the importance 

 of the nucleoli. In the large ganglion-cells of Doris, Pleurobranchus, 

 &c, nucleoli pass from nucleus to cytoplasm, migrate to the periphery, 

 and pass out with a constricted-off portion of cytoplasm. It is a process 

 of ganglion-cell multiplication. In Doris the mother-cell persists, in 

 Pleurobranchus it is sacrificed to making the daughter-cells, whose 

 nuclei are formed from the nucleoli. In young dogs and cats the 

 chromophiluus cells of the spinal ganglion-cells behave in a similar 

 fashion. 



Development of Cilia.lf — Dr. A. Gurwitsch has studied this in the 

 ciliary cells of the pharyngeal epithelium and tela chorioidea of sala- 

 mander larvse. In the former, the cilia appear first and the basal 

 corpuscles later on, both apparently quite independent of the centro- 

 somes. The second case is rather more difficult, but it seems probable 

 that cilia and basal corpuscles arise as independent differentiations of 

 the same plasma. 



* Anat. Anzei?.. xvii. 0900) pp. ?3-44 (2 pis.). 

 t SB. bohm. Ges. Wiss., July 1899. 



j Atti Soc. Venet.-Trent. Sci. Nat., 1S98 (published 1899) pp. 382-8 (1 pi.). 

 § Anat. Anzeig., xvi. (1899) pp. 334-42 (2 figs.). 

 || Jahresber. Schles. Ges., lxxvi. (1899) 2" Abth., pp. 23-7. 

 1J Anat. Anzeig., xvii. (1900) pp. 49-58 (5 figs.). 



