208 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
site. Since making the experiment Dr. Stiles has learnt that it is the 
custom among many American farmers to make use of their hogs to 
rid their grounds of these grubs. It is quite possible that of the 91 
known American species of Lachnostema others as well as L. arcuaia 
may serve as intermediate hosts for the same parasite. It has been 
objected that Melolontha vulgaris is a phytophagous Insect, and so also 
is Lachnostema, but as the plants which they affect are the tender 
shoots found under manure patches, it is easy to see how they may 
become infected. 
y. Platyhelminthes. 
Nervous System of Nemertinea.* — Herr O. Burger gives an account 
of his further investigations into the nervous system of Neinertines. He 
has been able to convince himself of the presence of unipolar ganglion- 
cells, the process of which he followed into the central substance, where 
he saw the fibre mix with the central cord, and then pass into the dermo- 
muscular tube. His views as to the neuro-chord are somewhat altered, 
for he believes that even in unarmed forms it represents a single axis- 
cylinder which does not divide into several. 
Though the ganglion-cells of Neinertines are, like those of Astacus, 
unipolar, there are some differences. In Astacus the (relatively few) 
secondary processes arise only in the more proximal portion of the trunk 
process, while in Cerebratulus their origin is more extensive, and there 
are, consequently, a number of them. The secondary group of Cerebra- 
tulus has only very fine granules, and is thereby markedly distinguished 
from Astacus where the branches have relatively well developed thick- 
enings. Like Astacus and Homarus, Cerebratulus has nerve-fibres, the 
sheath of which is devoid of myelin, and has constrictions externally to 
which nuclei are set. The nerve-fibrils to the muscular fibres of Dre- 
panophorus branch in just the same way as the nerve-fibres which go to 
the thoracic muscles of the Crayfish are figured by Retziusas branching. 
The dotted central substance of the lateral trunk of Cerebratulus is, in 
structure, essentially different from that of the ventral medulla of 
Astacus; there is a striking preponderance of connective-tissue in the 
lateral trunk, and there is not the same mode of branching of the 
secondary processes. 
On the whole, however, tho similarity in structure between the 
nervous elements of Homarus and Astacus and of the Nemertinea is very 
great, though the arrangement is, of course, different. 
The author observed, in the Nemertinea, cells intercalated between 
the nerve-fibre and the epithelial cell which it innervated. Similar cells 
may often be detected, after maceration, in all groups of animals, and 
have been variously named — nucleus, ganglion-cell or nerve-cell ; they 
should be always called nerve-cells, and never ganglion-cells, for these 
are fundamentally different structures. The nerve-cell is to be regarded 
as a cell which conveys the stimulus and has no power of independent 
reaction ; a ganglion-cell, on the other hand, is stimulated at one end of 
a path, and only stimulates if it communicates with other ganglion-cells. 
There is no evidence in the Nemertinea of a double origin of the 
nerves. 
* Mittlieil. Zool. Stat. Neapel, x. (1891) pp. 20G-51 (2 pis.). 
