16 



On the Nervous System of Aurelia aurita. [Jan. 10, 



narial passage, and are termed by me the "septo-maxillaries," attain 

 their highest development in serpents and lizards. I do not find them 

 in the tortoises and crocodiles, but they re-appear — very small — in 

 carinate birds, in connection, as in the snakes, with the vomers and 

 labial cartilages. 



In the mandible the upper part of Meckel's cartilage ossifies as the 

 " articulate," and now we get the full number of the splints, namely, 

 jl ve — the dentary, sphenial, coronoid, angular, and surangular. The 

 pier is a single bone, the quadrate. These six pairs of bones forming the 

 free mandible occur also in the lizards, crocodiles, and in most birds 

 In tortoises they are fewer, and in gallinaceous birds I have failed to 

 find the coronoid piece at any stage. 



The tono-ue of the- snake shows no cartilage in its structure ; neither 

 cerato-hyal, basi-hyal, or thyro-hyal, have appeared in any of my 

 dissections. 



IV. " Observations on the Nervous System of Aurelia aurita." 

 By Edward Albert S chafer, Assistant Professor of Phy- 

 siology in University College, London. Communicated by 

 W. Sharpey, M.D., LL.D., F.R.S. Received October 31. 

 1877. 



(Abstract.) 



The author describes the nervous system of Aurelia as consisting, in 

 addition to the lithocysts and certain tracts of specially modified epi- 

 thelium in their neighbourhood, of an interlacement of nerve-fibres 

 covering the whole of the under surface of the umbrella and lying 

 between the ectodermal epithelium and the muscular sheet. Each 

 nerve-fibre presents near the middle of its course a nucleated enlarge- 

 ment in the shape of a bipolar nerve-cell, which is thus interpolated in 

 the course of the fibre. With regard to these nerve-fibres it is re- 

 marked — firstly, that they are of limited length, seldom exceeding four 

 millimetres ; secondly, that they never come into actual continuity 

 with other fibres, although they frequently run closely parallel for a 

 certain distance, and often form extremely intricate interlacements by 

 the coming together of a number of fibres. The fibres occasionally 

 branch. They are described as ending generally by finely-tapered 

 extremities, which are in close contact with the substance of the mus- 

 cular fibres, but sometimes the termination of the nerve is dilated into 

 a flattened nucleated expansion, probably a primitive form of motorial 

 end plate. 



The structure and relations of the lithocysts are then treated of. 

 The iithocyst is described as consisting of an ectodermic covering and 

 an endodermic core, the two being nearly everywhere separated by a 



