ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
53 
(a) The sensory plates are from the first two distinct structures. As 
is well known, they give origin to the tentacles, the cerebral ganglia, 
and the cerebral tubes which form the accessory lobes. In Limax , the 
oral or subtentacular palps arise as a third, modified pair of tentacles, 
and tentacles have nothing to do with a velum, but solely with the sen- 
sory plates. It does not follow, of course, that all the subtentacular or 
labial palps of Gastropods are of this nature; some may be derived 
from the velum like the labial palps of Lamellibranchs. 
(b) The foot in Succinea (as in Patella) has originally a paired rudi- 
ment, and the author regards this as primitive. After the closure of 
the typically elongated blastopore, which separates the two rudiments of 
the foot, fusion of the two parts occurs. A podocyst, or embryonic cir- 
culatory organ, is absent in Succinea. The “ Nachenblase ” is not an 
organ, but merely a region to which the contractions of the podocjst 
give a false appearance of contractility ; in Succinea it shows no hint of 
movement. 
(c) The mantle or shell-area. At a very early stage the epithelium 
in the centre of the shell area in Clausilia sinks in to form a closed sac. 
This forms the shell-gland within which an embryonic shell is formed. 
A further insinking in the centre of the mantle area meets the shell-sac, 
and the rudimentary shell is exposed. This confirms an old observa- 
tion of Gegenbaur’s, and Schmidt finds that in Succinea also the originally 
internal shell comes secondarily to the surface. 
Development of Pulmonata.* — Dr. R. Heymons makes a few re- 
marks on Dr. von Erlanger’s lately published studies on the development 
of the Pulmonata. He objects to Erlanger contradicting his views, not 
on the ground of independent investigation, but because his view on the 
position of an organ and its unpaired condition appears to him to con- 
tradict it. From Dr. Heymons’s remarks it would appear that he has 
already considered the chief objections to Erlanger’s view, and naturally 
is vexed that they have not been accepted. 
Attractive Sphere in Fixed Cells of Connective Tissue, f — Dr. 0. 
De Bruyne has taken up the study of this subject, which has been, as 
our readers know, the object of numerous researches since the time when 
M. E. van Beneden, studying the egg of Ascaris megalocephala, indicated 
the importance of the attractive sphere. The present author has been 
occupied with this sphere, as he met with it in the fixed connective tissue 
cells in the interstitial tissue of the liver and of the gonad of Paludina 
vivipara. The sphere of these cells is generally composed of a mass, 
which is either homogeneous or finely granular, and which may reach, 
but rarely surpasses in size, the dimensions of the nucleus. From this 
mass, as a centre, there radiate out in all directions filaments which form 
a widely open plexus. They reach the surface of the cell, where they 
end freely in the cytoplasm. The sphere is found situated in the imme- 
diate neighbourhood of the nucleus, and is sometimes so closely applied 
to it that it is very difficult to see the line of separation. The author 
recommends the tissue which he has chosen, as being very suitable for 
researches of this kind, and asserts that it is better adapted for the 
subject than many which have been selected by other investigators. 
Zool. Anzeig., xviii. (1895) pp. 400-2. 
f Bull. Acad. Beige, lxv. (1895) pp. 241-56 (1 pi.). 
