22 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
“ plates,” each “ plate ” travelling in an opposite direction. The inter- 
zonal filaments are, according to this view, the actual continuations of 
the archiplasmic filaments, hut, instead of consisting of a single system, 
as at either end of the spindle, they are composed of two systems, each 
dovetailing with the other and growing in contrary directions. 
The author’s object is to show that the origin of the spindle, its 
behaviour towards the nucleus, the formation of the equatorial chromatic 
“ plate,” the separation of the daughter-plates, and the formation of the 
interzonal filaments, are the continuation of one and the same process ; 
that there is no reversal of activity in the middle, and no need for the 
introduction of several hypothetical factors. 
An account is next given of the cleavage of the ovum in Loligo 
Pealii, in which particular attention is directed to the inequalities 
therein exhibited. The cause of unequal cleavage appears to the author 
to he internal, due to the peculiarities of the particular protojdasmic 
structure which composes the segment or segments. Differences are 
due, it would seem, to the slight qualitative inequalities induced by the 
first division. If tbis be so it follows that the earlier cleavage-processes 
are the more fundamental, and, from the morphological standpoint, more 
significant than those that follow them. As eggs from the same animal 
show similar variations in cleavage, it is possible that this tendency to 
vary may become hereditary. 
Illex eblanae.* — Mr. W. E. Hoyle has a note on this inadequately 
known Cephalopod, a specimen of whioh was lately taken near Plymouth. 
He finds that the form described by Ball as Loligo eblanse is really a 
member of Steenstrup’s genus Illex. After giving a revised diagnosis 
he describes an interesting form of hectocotylization. The alteration 
aifects both arms symmetrically in their basal portion, hut the right 
arm only is modified to the tip. About 2 cm. from the base of each arm, 
instead of a sucker, there is a flattened bract-like appendage, growing 
out from a broad base. Its distal margin is slightly notched, and has a 
sharp tooth at its inner extremity. On the inner margin of the arm are 
three conical teeth, which feel almost cartilaginous. From a comparison 
of four specimens of different sizes the author is led to conclude that on 
the hectocotylized arms suckers are normally developed, and gradually 
disappear as the animal approaches maturity. 
■y. Gastropoda- 
Development of Paludina vivipara.f — In the second part of his 
memoir Dr. R. v. Erlanger treats first of the development of the nervous 
system. Special attention is directed to the fact that all the ganglia arise 
quite separately from one another, and this is true even of those that are 
paired. The cerebral ganglia are the first to be formed, then the pedal, 
directly afterwards, and almost simultaneously, there appear the pallial 
and buccal ; these are followed by the two intestinal ganglia, and last 
of all come the visceral. The progressive development from before back- 
wards is also seen in the formation of the commissures and connectives. 
It is difficult to decide whether the pallial ganglia are in closer relation 
* Journ. Mar. Biol. Ass., ii. (1891) pp, 189-92 (3 figs.). 
t Morphol. Jahrbucb, xvii. (1891) pp. 636-80(2 pis.). Zool. Anzeig., xiv. (1891) 
pp. 280-3. 
