285 
has figured the parts given in fig. 5 in his work on the nervous 
system of Annulosa. The presence of the second commissure 
or nerve-collar (stg) is very remarkable. It is not present 
in Ch. Limncei, or, if represented, not sufficiently differentiated 
from the surrounding tissue to be apparent. In the larvae of 
Ch. Limruei the nerve-tissue is homogeneous. The chain of 
ganglia drawn from the first suboesophageal is important in 
connection with the question as to the number of somites in- 
tervening between the cephalic bristles and the first abdominal 
fasciculi. It is not till we get as far down the cord as that 
lettered 1 br. (in connection with the first pair of abdominal 
fasciculi) that the normal form of ganglion, which persists 
throughout the rest of the body, commences. Two normal 
ganglia are probably represented by ce and st respectively on 
the oesophagus and stomach, and hence, it may be inferred 
— two somites, which have become fixed and modified into 
this intra-fascicular region ; but it seems that this is not a 
necessary conclusion. We may suppose that this region 
never has been or would be segmented, and that its ganglia 
are due, not to an arrested or fused condition of tertiary aggre- 
gation, but to development of ganglionic nerve-tissue at various 
points in the nerve-strand of a secondary aggregate — that is 
to say the secondary aggregate to which each segment of 
Chaetogaster partially corresponds in an arrested condition 
(i. e. minus a head). The separation into gangliform masses 
in the nerve-cord from sphg. to 1 br. may indicate superin- 
duced and not constitutional segmentation. The separation 
of these two forms of segmentation is a matter of great 
difficulty, and, at the same time, most important for the 
morphology of the Annulosa, and equally for that of the 
Vertebra ta. 
Notf.s on the Thysanura. By Sir John* Lubbock, Bart., 
F.R.S., V.P. Linn. Soc., &c. &c. (Abstract of Paper, 
No. 4, read to the Linneau Society.) 
Sir John began by adding four more species to the list of 
British Thysanura, which now comprises about fifty species, 
of which only fourteen were recorded as British when he 
began to study the group. Three out of the four now added 
are Continental species ; the fourth does not agree with any 
