TRANSACTIONS OF THE SECTIONS. 125 



Physiology. 



On the Ultimate Arrangement of Nerves in Muscular Tissue. 

 By Professor Beale, M.B., F.R.S. 



On the Leptocephalidae. By Professor V. Carus, Leipzig. 



Dr. Kaup places the European species of this highly interesting family in four 

 generic groups, — Esunculus, Hyoprorus, Tihirus, and Leptocephalus. It strikes at 

 first, to find amongst the " Apodal" fishes a form with well-developed ventral fins, 

 viz. Esunculus, similar to the rest only in its transparency, and in wanting the 

 generative organs, differing from them also in the distinctness of the dorsal and anal. 

 Among the rest there are two well-established genera, Tilurus with its hair-like 

 tail, and Leptocephalus. According to Dr. Kaup, Tilurus contains two species, tri- 

 ck iitrus and Hissoi, but both are probably the same, as Rissoi is most likely founded 

 on a mutilated specimen. The chief character is taken from the tail here being 

 shorter ; Dr. Kaup adds, however, himself, " perhaps defective in the tail." The 

 species of the genus Leptocephalus are to be classed in two groups ; the type of the 

 first is L. Morrisii, that of the other is Helmichthys diaphanus of Ralinesque. The 

 former have the body compressed, the latter rounder, earth-wormlike body. L. Mor- 

 risii and L. Spallanzanii differ only by the height of the former, upon which 

 argument one cannot lav much stress, as exact measurements of many individuals 

 give very considerable differences in the relative height and length of the whole 

 bodv, as well as of the head and the other parts. The species of the second group, 

 L. punctatus, diaphanus, Kbttiheri, Gegenbauri, Bibroni, and Yarrelli, are representa- 

 tives of at most two species, punctatus and diaphanus. The chief distinction is 

 taken from the relative position of the intestinal outlet. I did not find in two 

 specimens out of some dozens the same position of this orifice ; nor are the row of 

 black points, which characterize the L. punctatus, always so well developed, that 

 they could be taken as a good character. However, the habits differ in some respect 

 from that of the rest. L. longirostris reminds of Hyoprorus ; the latter is probably 

 nothing but a further developed or an earlier form of the L. longirostris, L. stenops, 

 and L. brerirostris : the two last European species of Dr. Kaup's Synopsis I know 

 only by his figures, but I am very much inclined to believe that they are to be 

 judged like the others. 



Taking together the anatomical structure of the whole group, the absence of ge- 

 nerative organs, the structure of their skin, their skull, their vertebral column, taking 

 furthermore into consideration the variability of both the zoological characters and 

 the proportional measurements, I cannot but come to the conclusion that all these 

 fishes are nothing but larval forms of others. The developed full-grown species to 

 winch all of them, except the Esunculus Costal, belong, are most likely among the 

 Ophidians, or other compressed forms {Cepola, and so on). Although lam not yet 

 able to state with certainty what species or even genera are to be studied in their 

 development as giving Leptocephalideous larva?, yet I feel quite sure that the 

 family under consideration will ere long be era?ed from the Sysiema Naturae, just 

 as the Ammoccetes has been excluded from the benefit of being reckoned a full- 

 grown member of the Animal family. 



On the Value of '" Development" in Systematic Zoology and Animal 

 Morphology. By Professor V. Carus, Leipzig. 



Although there may be some who will object to ray bringing forward a topic of 

 general bearing, and who would prefer to have stated some special facts and details 

 new to science, yet I think that meetings of this kind afford the best opportunity 

 of clearing up, or at least recalling to mind, questions which we are all familiar with, 

 the true bearing of which, however, we are very apt to lose sight of. Since Cuvier 

 laid the foundation-stone of our modern classification of animals, there has been 

 within the last thirty-three years much labour bestowed upon the mending his 

 system, and looking for new characters by which his classes and orders may be 

 either altered and arranged in a somewhat different manner, or still better founded. 

 However, we look up to him not only as the reformer of the classificatory branch of 



