The anatomy of the common squid, Loligo pealii, Lesueur . ivepairs of connectives to the five pairs ofbrachial ganglia. Connectives unite thefirst and second, the second and third,the third and fifth brachial ganglia, andwith the commissures between the gang-lia of the first pair and the fifth pairform the branchial nerve-ring. Careful search has failed to reveal any connectionbetween the ganglia of the fourth arms (tentacles) and this ring. The pleural ganglion, viewed externally, is well marked and is readilydistinguished from the cerebral ganglion on one hand and from the pedal andvisceral
The anatomy of the common squid, Loligo pealii, Lesueur . ivepairs of connectives to the five pairs ofbrachial ganglia. Connectives unite thefirst and second, the second and third,the third and fifth brachial ganglia, andwith the commissures between the gang-lia of the first pair and the fifth pairform the branchial nerve-ring. Careful search has failed to reveal any connectionbetween the ganglia of the fourth arms (tentacles) and this ring. The pleural ganglion, viewed externally, is well marked and is readilydistinguished from the cerebral ganglion on one hand and from the pedal andvisceral ganglia on the other, but a study of the minute anatomy of the socalled ganglion shows that there is very little ground for calling the mass offibres in which a few nerve cells are scattered a ganglion. It is really a massof nerve tracts passing, a) between the optic lobes through the base of thecerebral ganglion, b) from the optic ganglion to the cerebral and pedal ganglia,.and c) from the cerebral to the pedal and visceral ganglia. Nevertheless, it is. Fig. 15, 70 convenient to retain tlic term, ^an^iiun, as a name Ibr tliis region of tlieoesophageal ring. The pleural and cerebral ganglia (with a slight exception mentioned below)consist of small cells whose nuclei vary in diametei between 4 and 7 micia a,ndwhose cytoplasm is scarcely discernable, the tissue having a granular appearanceunder a low power of the microscope. A small lobe of the ceiebral ganglion,forming the lower part of its front end and surrounding the tracts which passout into the cerebro-buccal and cerebro-propedal connectives, differs from the restof the ganglion in that the cells are larger. The nuclei are from 5 to 18 micrain diameter and the diameter of the cytoplasm is twice or three times that ofthe nucleus. In contrast to these ganglia, all the other ganglia of the squid havea greater or less proportion of large cells whose nuclei vary from 13 to 20 micrain diameter and whose cytoplasm has a diame
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