ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
629 
immediately before tlie formation of the polar body. The nucleolar 
substance the author regards as a product of the active metabolism of 
the nuclear chromatin. The formation of tetrads in the nutritive cells 
is to be regarded as a degenerative process, but the nuclei of these cells 
as a whole play an important part in the nutrition of the egg. The 
yolk-nuclei of the egg are most nearly related to nucleolar substance. 
Annulata. 
Viviparity in an Annelid.* — MM. F. Mesnil and M. Caullery have 
already described the polymorphism of Dodecaceria concharum (Ersted, 
two forms of which (R and 0) undergo a metamorphosis of which 
there is no trace in a third form (A). They have now found out that 
this form A is viviparous and parthenogenetic. There is no hint of 
males belonging to this A form. The larvae appear to be liberated by 
the rudimentary segmental organs. It seems to be a case of what 
Chun has called “dissogony.” 
Structure of an Australian Land-Leech.f — Miss Ada M. Lambert 
gives a careful account of a species which Blanchard has named Philse- 
mon pungens. It bears more resemblance to Hsemadipsa than to any 
other genus of Gnathobdellidm. It possesses five pairs of eyes, a point 
in common with Mesobdella, but differing from Xerobdella. It differs, 
however, from all three genera in having only two tooth-plates. 
Histology of Ehynchobdellidse.J — Herr Emil Bayer, in the course 
of his researches on the anatomy and development of these leeches, has 
made some observations on the hypodermis, sense-organs, and skin- 
glands. He finds that the cells of the hypodermis show a distinct 
division into two regions, an inner filled with granular protoplasm, and 
an outer which shows vertical fibrillation. The fibrillation is apparently 
the result of a modification of the protoplasmic network, and is asso- 
ciated with the development of a cuticle. It is comj>arable to a similar 
structure in the epidermal cells of Gordius. As to the sense-organs, 
the cup-shaped organs in the Rhynchobdcllidae are scattered irregularly 
over the whole surface of the body. There are also hitherto unde- 
scribed sense-organs of very remarkable structure in the Rhynclio- 
bdellidae, notably in Glossosiphonia sexoculata. In this species the 
sense-organs may be seen under slight magnification as little cones 
scattered over the dorsal surface. Each consists of two cells ; the outer, 
the sense-cell proper, is a modified hypodermis cell with a large nucleus, 
and ending in exceedingly fine cilia which penetrate the cuticle. The 
lower cell is a muscle-cell, capable by its contraction of acting on the 
sense-cell so as to telescope this within itself. It is divided into an 
upper transversely striated region and a lower clear area containing 
the nucleus. These remarkable sense-organs are described in detail, 
the description being illustrated by admirable figures. They are ap- 
parently tactile organs, and their position and number are associated with 
the habits of the species. The paper ends with some account of the 
hypodermal and sub-hypodermal glands, which are chiefly distinguished 
from one another by the degeneration of the nucleus in the former. 
* Comptes Rendus, cxxvii. (1898) pp. 486-9. 
f Proc. R. Soc. Victoria, x. (1898) pp. 211-35 (5 pis. and 5 figs.). 
% Zeitsclir. f. wiss. Zook, lxiv. (1898) pp. G 18-96 (?> pis. and 10 figs.). 
