TBANSACTIONS OF SECTION D. 693 



We arrive, then, at the curious result that the innervation of the ceratal 

 processes is not the same in all these Nudibranchs. In Poh/ccra, Ancula, Tritonia, 

 and Dendronotus the epipodial nerves arise from pleural ganglia, or from th» 

 ventral and posterior parts of cerebro-pleural masses; while in Eolis the chief 

 epipodial nerves are from the pedal ganglia, hut there are also smaller nerves from 

 the pleurals. lu the ordinary Rhipidoglossate gastropod, such as Trochus, the 

 epipodial ridges and processes are supplied, according to Pelseneer, by nerves 

 arising from the dorsal part of the elongated pedal ganglia. So, judging from the 

 nerve supply alone, it might be said that the cerata of Eolis are pedal in their 

 nature, and homologous with the epipodial processes of Trochus, while those of 

 Ancula and the rest are totally distinct structures of pallial ' origin. But these 

 dorso-lateral processes in the various Nudibranchs are so much alike in their 

 relations, and are connected by such series of gradations, that it is difficult to 

 believe that they are not all homologous, and the presence of the accessory 

 epipodial nerve in Eolis arising from the pleural ganglion suggests the possibility 

 of another explanation, viz., that these outgrowths, starting at first as pedal 

 structures innervated by nerves from the pedal ganglia, may have acquired, 

 possibly as the result of having moved further up the sides of the body, a supple- 

 mentary nerve supply from the adjacent integumentary nerves arising from the 

 pleural ganglia, and this supplementary supply, while remaining subordinary in 

 Eolis, may in the other types have gradually come to supplant the original 

 epipodial nerves, which are now no longer found in such forms as Polycera and 

 Ancula. This is at present only a suggestion, which, however, we hope to be able 

 either to disprove or support by the examination of the nerves of a number of 

 additional Nudibranchs. 



7. Exhibition of a Neiu Apparatus for Opening and Closing a Tow-Net hy 

 Electricity. By W. E. Hoyle and L. F. Masset. 



8. Exhibition of, and Eemarlcs ujwn, some Young Specimens o/ Echidna 

 acaleata. By Professor "W. N. Parkek, Ph.D. 



The specimens are from the collection of the late Professor "NV. K. Parker, who 

 received them from Dr. E. P. Ramsay, Curator of the Australian Museum, 

 Sydney. They are much curved towards the neutral side, the snout pointing 

 backwards, and the tail, in the older of the two stages, forwards. The younger 

 atage measures along the dorsal curve, from the end of the snout to the tip of the 

 tail, 12 cm., the greatest diameter of the body being 3 cm.; the corresponding 

 measurements of the older stage are respectively til 5 cm. and 6 cm. In the 

 latter the body is covered with short scattered bristles. In both stages the snout 

 is very similar in form to that of Ornithorliynchus, and is covered by a thick 

 horny layer, but in other respects the specialisation characteristic of Echidna is 

 already apparent. The gape is narrow, and extends only a short distance dowTi 

 the snout, and the manus, even in the younger stage, is already much larger and 

 stronger than the pes. The tail is short and conical. There is no caruncle, or 

 ' egg-breaker,' in the snout, such as is seen in Ornithorhynchus. 



A few points in the structure of the fore part of the head in the older stage 

 were described. The mouth has the narrow and tubular form seen in the adult, 

 and the long tongue has a horn)' tip. The glands in relation with the mouth and 

 nose are very numerous. There is no trace of any teeth-rudiments, and in many 

 other respects the structure of the head shows extreme specialisation. Jacobson's 

 organ is large and highly developed ; a well marked * turbinal ' is present in it. 



' I.e. dorsal to the foot, whether there is a distinct pallium present or not. 



