291 
7) Ross, Ueber die Zahnentwickelung der Menschen. Schweizer Viertel- 
jabrschr. f. Zahnheilkunde, 1892. 
8) Kürentuar, Das Gebiß von Didelphys. Anat. Anz., 1891, p. 658—666. 
9) Rosz, Ueber d. Zahnentwickelung d. Beuteltiere. Anat. Anz., 1892, 
p- 639—650, 693—707. 
10) —, Ueber die Zahnentwickelung von Phascolomys Wombat. Sitzungsber. 
d. Kgl. Pr. Akad. d. Wissenschaften zu Berlin, 1893. 
11) —, Ueberreste einer vorzeitigen prälactealen und einer vierten Zahn- 
reihe beim Menschen. Oest.-ung. Vierteljabrsschrift für Zahnheilkunde, 
Jahrg. XI, Heft 11. 
12) Woopwarp, M. J., On the teeth of the Macropodidae. Proc. Zool. Soc., 
1893. 
13) Ross, Ueber die Zahnentwickelung des Rindes. Morph. Arbeit., Bd. VI, 
Heft 1. 
14) Woopwazp, M.J., On the Dentition of certain Insectivora. Proc. Zool. 
Soc., 1896. 
15) Kükentaas, Ueber die Entstehung und die Entwickelung des Säuge- 
tierstammes. Biol. Centralbl., Bd. XIII, 1892, p. 400—413. 
16) Woopvwarp, M. J., On the Succession and Genesis of Mammalian Teeth. 
Science Progress, 1894, p. 438.. 
17) Tıms, Notes on the Dentition of the Dog. Anat. Anz., 1896, p. 35. 
18) Tuomas, On the Homologies and Succession of the Teeth in the Da- 
syuridae. Phil. Trans., Vol. CLXXIX, p. 443—462, 1887, 
Nachdruck verboten. 
Centrosome and Sphere in Certain of the Nerve Cells of an 
Invertebrate !). 
By Marecaret Lewis, 
Student in Radcliffe College, Cambridge, Mass., U.S.A. 
With 11 Figures. 
In August 1895 I found a new species of worm belonging to 
the annelid family Maldaniae, which will be described elsewhere. It 
is closely related to the well known form Clymenella torquata, with which 
I found it associated in one of the sand flats of Vineyard Sound. 
During the past winter, while studying the finer anatomy of the 
nervous system of this worm, I became interested in structural conditions 
of certain of the nerve cells which were found to be constant. I could 
find no account of a similar condition in any of the papers consulted 
1) Contributions from the Zoölogieal Laboratory of the Museum of 
Comparative Zodlogy at Harvard College, under the direction of E. L. 
Marx, No. LXVIII. 
