ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
639 
are “ only sham.” In the male, similarly, the only true orifices are on 
the fifth pair of legs, those on the third pair being closed. There is some 
but not adequate evidence that the testis shows hints of eggs. The 
author goes on to notice the subterranean habits of the animal and its 
autotomy. 
South African Phyllopods from Dried Mud.* — Prof. G. 0 . Sars 
describes Apus numidicus Grube, hatched out as a nauplius from the 
egg ; Streptocephalus gracilis sp. n. ; Str. purcelli sp. n. ; BrancMpodopsis 
hodgsoni g. et sp. n., which approaches Branchipus and Branchinecta ; 
Estlieria elizabetlise sp. n. ; and Leptestheria siliqua sp. n. 
Annulata. 
Cell-Lineage in Annelids and Polyclades.f — Prof. E. B. Wilson 
returns to an interesting suggestion which he made some years ago, 
that a pair of rudimentary cells observed in the early embryos of Aricia 
and Spio were to be regarded as vestiges of an ancestral type of develop- 
ment in which they were represented by a group of larger functional 
cells, such as are still found in the embryo of Nereis. The vestigial 
cells in question represent the posterior part of the entoblast-plate. 
Fresh investigations show that the three forms — Crepidula , Nereis , 
and Aricia — form a progressive series in which the entoblastic part of the 
mesentoblast cell is reduced from more than half the bulk of the cell to 
an insignificant vestige ; and the facts support the view r that the primary 
mesoblasts or mesoblastic pole-cells of Annelids and Molluscs must be 
regarded as derivatives of the archenteron. “ The vestigial cells of 
Aricia, Spio, Amphitrite, and Planorbis would seem to represent the last 
traces of such archenteric origin of the teloblasts ; ” and the bearing of 
this on the possible relation between the teloblastic and enterocoelic 
modes of mesoblast-formation is obvious. 
After discussing the micromere-quartets in Annelids, Molluscs, and 
Polyclads, and in Leptoplana in particular, the author indicates the 
general interest of the phenomena. ( a ) They suggest that development 
may exhibit ancestral reminiscence as clearly in the cleavage of the 
ovum as in the later formation of tissues and organs. ( b ) They seem 
on the whole to emphasise the importance of cell-formation in develop- 
ment, recent reaction notwithstanding. 
Nervous System of Polychaeta.f — Miss M. Lewis has studied this 
in two of the Maldanidte, Axiothea ( = Clymenella) torquata and Clymene 
producta sp. n. She finds that Ley dig’s fibres in Annelids are true 
nerve-fibres, the sheath being comparable to the medullary sheath of 
nerve-fibres in Vertebrates, and the contents to the axis-cylinder. The 
fibres result from the union of the direct processes of giant ganglion- 
cells. The cells which give rise to Leydig’s fibres show peculiar struc- 
tural conditions,' in the possession of a nucleus always eccentric in posi- 
tion, and of other structures more central in position, the centrosome 
and the attractive sphere. Parts of the peripheral nervous system end 
* Arch. Matli. Naturvidenk. Christiania, xx. (1898) 43 pp., 4 pis., and 23 pp., 
3 pis. See Zool. Centralbl., v. (1898) p. 456 and p. 508. 
t Ann. New York Acad. Sci., xi. (1897) pp. 1-27 (7 figs.). 
% Proc. Amer. Acad. Sci., xxxiii. (1898) pp. 225-68 (8 pis.). 
