Miscellaneous. 245 



very visible upon the back of the muscles. The ganglia, generally 

 three in number, like the hard pieces, are better formed than in 

 Pliiline. 



Aplijsia has an enormous crop upon which we can easily trace 

 the two great stomachal nerves, which, from point to point, are 

 united by slender nerves the anastomoses of which form a network 

 of not very close meshes. Towards the bottom the muscular tissue 

 is much thickened, and its rigidity shows clearly that it is very 

 powerful. Within the mucous membrane is covered with pyramidal 

 hard pieces, arranged in several rows and of several sizes without 

 being further differentiated. This part is the homologue of the 

 gizzard of Bulla and Philine. 



Here, as in the preceding examples, towards the superior limit of 

 this gizzard there exists a nervous ring, greatly developed and 

 formed by stout anastomotic branches transversely uniting the 

 gastric nerves. From this ring issue parallel branches, which 

 descend, innervating the muscles. Most frequently six of these 

 nerves may be counted. Towards the bottom their anastomoses are 

 less regular than above and their terminal branches pass to the 

 stomach and intestine. 



Thus, it will be seen, with the appearance of a masticatory appa- 

 ratus the number of the nerves and ganglia increases in proportion, 

 it may be said, to the actual development of the modified parts. 

 It is therefore not doubtful that in appearance there is a great 

 difference between the organs of innervation of the digestive tube 

 according as there is or is not a gizzard, that is to say, pieces 

 adapted for mastication. The ganglia and stomachal rings of Philine, 

 Aphjsia, &c. are quite special centres of innervation. Bat it would 

 not be legitimate to exaggerate their morphological importance ; 

 they are dependencies of the stomato-gastric centre, with which 

 they must be joined, instead of separating them from it. It is 

 evident that they are superadded and introduce no modification 

 into the interpretation of the stomato-gastric centre, which always 

 remains the same in its central part and is only modified in a por- 

 tion of the periphery to respond to new necessities when a masti- 

 catory apparatus is added to the digestive tube. 



In another memoir I shall show that there are cases in which 

 these observations are applicable even to the peripheral nervous 

 system dependent upon the cerebroid ganglia, and that, by a sort of 

 organic balancing, to employ the language of Geoffrey Saint-Hilaire, 

 the primordial ganglia lose in volume while still remaining perfectly 

 distinct, whilst the superadded cellular aggregations, irregularly 

 disseminated through the course of the nerves, form secondary 

 strengthening ganglia, which make up for the feeble development of 

 the primordial centres. — Comjites Rendus, October 4, 1886, pp. 583- 

 587. 



