A STUDY IN CARCINOLOGY. 29 
(les Macroures pour se I'approcher des Brachyures et la reduction qu'il presente 
dans le sens de la longueur, est un indice, non pas des affinites precises de 
I'animal, inais du degre d'evolntion cancerienne auquel il est arrive." If we 
accept this proposition, and for my own part I accept it withont reserve, 
it must follow that a crab with a nervous system of which the ganglia are 
more concentrated in the longitudinal direction is farther removed from its 
Macruran ancestry than one in which the ganglia are far less concentrated, 
and that tlie former cannot be a progenitor of the latter. 
Of the Raninidaj I have been able, thanks to the excellent state of preser- 
vation of the example sent me by Prof. Kishinoye, to make a thorough study 
of the nervous system of Ranina deiitata and a sufficient study of that of 
Lyreidns tridentattis, of which I possessed two well-preserved examples. 
I have also dissected the nervous systems of Notopus dorsipes and Notosceles^ 
cliimmonis, and was able to ascertain that they are of the same character and 
the ganglia fully as much extended in the longitudinal line as in Ranina 
and Lyreidus, but their state of preservation did not admit of great accuracy 
in making out details. 
PI. 4. fig- 8 is a drawing of the nerve-ganglion chain of Ranina dentata^ 
as seen from above, tlie whole sei'ies being represented as flattened out in one 
plane. PI. 4. fig. 9 shows the actual position of the nerve chain as seen 
from the side, and its relation to the endophragm;il skeleton. Owing to the 
deep infolding of the sternal apodemes of the posterior thoracic somites, 
the posterior thoracic ganglia and the abdominal ganglia closely applied ta 
them are directed nearly vertically upwards. 
The cerebral ganglion is relatively large and quadrangular in outline, and 
the ocular, antennulary, and antennary nerves are of large size ; otherwise it 
does not present any special features. A small pair of nerves passes forward 
to the rostrum. The circum-oesophageal connectives are long and stout. 
The small ganglia on either side of the oesophagus give off a fairly stout 
nerve to dilator muscles of the oesophagus as well as the more slender 
connectives of the stomatogastric system. The post-oesophageal commissure 
is well marked. The suboesophngeal ganglion mass is large and goblet- 
shaped in outline, as seen from above, and gives off five stout nerves on either 
side. These nerves are somewhat swollen at their origins, and the last two 
come off rather apart from the rest and give the appearance of originating- 
from a separate ganglionic centre. Otherwise the six ganglia supplying the 
mandibles, first and second maxillse, and thi-ee pairs of maxillipeds are 
indistinguisliably fused in the suboesopliageal mass. It will be noticed that, 
the mandibular nerve does not spring from the suboesophageal ganglion but 
from the circum-cesophageal connectives, some way in advance of the ganglion. 
The ganglion pair of the chelipeds is distinct, but so closely fused to the 
suboesophageal mass that the connectives uniting the two are indistinguishable. 
